Metal-doped nickel oxide active materials

ABSTRACT

A primary alkaline battery includes a cathode having an alkali-deficient nickel (IV)-containing oxide including metals such as Ni, Co, Mg, Al, Ca, Y, Mn, and/or non-metals such as B, Si, Ge or a combination of metal and/or non-metal ions as stabilizing dopants; a combination of metal ions as dopants; an anode; a separator between the cathode and the anode; and an alkaline electrolyte. The battery can be pre-discharged within one hour after assembly to decrease the open circuit voltage.

TECHNICAL FIELD

This disclosure relates to cathode active materials, and moreparticularly to metal-doped nickel (IV)-containing cathode activematerials.

BACKGROUND

Batteries, such as alkaline batteries, are commonly used as electricalenergy sources. Generally, a battery contains a negative electrode(anode) and a positive electrode (cathode). The negative electrodecontains an electroactive material (such as zinc particles) that can beoxidized; and the positive electrode contains an electroactive material(such as manganese dioxide) that can be reduced. The active material ofthe negative electrode is capable of reducing the active material of thepositive electrode. In order to prevent direct reaction of the activematerial of the negative electrode and the active material of thepositive electrode, the electrodes are mechanically and electricallyisolated from each other by an ion-permeable separator.

When a battery is used as an electrical energy source for a device, suchas a cellular telephone, electrical contact is made to the electrodes,allowing electrons to flow through the device and permitting theoxidation and reduction reactions to occur at the respective electrodesto provide electrical power. An electrolyte solution in contact with theelectrodes contains ions that diffuse through the separator between theelectrodes to maintain electrical charge balance throughout the batteryduring discharge.

SUMMARY

This disclosure features metal-doped nickel (IV)-containing cathodeactive materials, batteries containing the cathode active materials, anda method for improving post-storage performance (i.e., “shelf life”) ofthe batteries.

This disclosure features a method that can improve capacity retentionfor primary alkaline batteries including a cathode that includes adelithiated, metal-substituted (i.e., metal-doped) Ni(IV)-containingactive material, or an unsubstituted Ni(IV) active material. TheNi(IV)-containing active material includes a layered nickel oxide wherethe Ni ions in the crystal lattice are at least partially substituted byone or more metal ions. The one or more metal ions can help decreasegeneration of oxygen gas from decomposition of the alkaline electrolyteby Ni(IV) during storage at ambient (e.g., 25° C.) and elevated (e.g.,45° C., 60° C.) temperatures. The metal ions can include transitionmetal ions and/or non-transition (e.g., main group, rare earth).

The method can include at least one preliminary conditioning step duringa battery manufacturing process where, immediately after assembly (e.g.,within about one hour of assembly), the battery can be partiallydischarged at a constant discharge rate (e.g., 5 to 100 mA/g) through anexternal resistive load for a sufficient period of time so as to consumeabout 1-15% (e.g., about 5-10%, or about 1-5%) of the total designcapacity of the cell. After pre-discharge, the cell can be held for aperiod of time at ambient temperature (e.g., 25° C.). The batteryconditioning can lower the initial OCV, decrease the initial rate ofoxygen evolution, and/or decrease the total amount of oxygen generatedby decomposition of electrolyte. The batteries can have greater totalspecific discharge capacity, decreased initial OCV, decreased internalgas pressure, and improved capacity retention after storage forprolonged periods at ambient and elevated temperatures, when compared toalkaline batteries with cathodes including delithiated, non-substitutedNi(IV)-containing layered oxides as active materials.

For example, after pre-conditioning, the OCV value of theNi(IV)-containing cell can be within a range (e.g., 1.65 to 1.75 V) thatis acceptable for consumer alkaline cells. The method can reduce aninitial rate of oxygen evolution that can result from a breakdown of analkaline electrolyte. In some embodiments, capacity retention ofpre-discharged Ni(IV)-containing alkaline cells, after storage for 1week at ambient temperature, can be up to 90% of the fresh capacity(i.e., a capacity measured within 24 hours after assembly). The primaryalkaline battery can have decreased internal gas pressure after storagefor a prolonged period of time at ambient and elevated temperatures.

In one aspect, the disclosure features a method of making a primaryalkaline battery, including partially discharging an assembled batterywithin about one hour of cell closure; maintaining the partiallydischarged battery for a period of time ranging from 1 to 24 hours at atemperature in the range of 25 to 70° C. to provide a pre-dischargedprimary alkaline battery; wherein the pre-discharged battery has an opencircuit voltage value of less than or equal to 1.75 V at 25° C.

In another aspect, the disclosure features a battery, including acathode comprising an oxide having a formulaA_(x)Ni_(1-y-z-w)Co_(y)M^(a) _(z)M^(b) _(w)O₂; an anode; a separatorbetween the cathode and the anode; and an alkaline electrolyte, whereinA is an alkali metal, M^(a) is a metal dopant, M^(b) is a non-metaldopant, 0≦x≦0.2, w is 0, or 0≦w≦0.02 and 0.02≦y+z≦0.25, wherein thebattery has an open circuit voltage value of from 1.65 to 1.75 V.

Embodiments of the battery may include one or more of the followingfeatures.

In some embodiments, the pre-discharged battery has a capacity retentionof at least 95 percent of the capacity of a battery discharged within 24hours after manufacture, after storage for at least one week at 25° C.The pre-discharged battery can have a capacity retention of at least 90percent of the capacity of a battery discharged within 24 hours aftermanufacture, after storage for at least one week at 45° C. Thepre-discharged battery can have a capacity retention of at least 85percent of the capacity of a battery discharged within 24 hours aftermanufacture, after storage for at least one week at 60° C.

In some embodiments, the pre-discharged battery has a decrease in oxygenevolution of at least 50% compared to a freshly assembled battery.

In some embodiments, the pre-discharged battery has an open circuitvoltage value of from 1.65 to 1.75 V at 25° C. The battery can bepartially discharged by 15 percent or less of a total battery designcapacity within 24 hours after manufacture (e.g., the battery can bepartially discharged by 10 percent or less of a total battery designcapacity within 24 hours after manufacture, the battery can be partiallydischarged by 7.5 percent or less of a total battery design capacitywithin 24 hours after manufacture, the battery can be partiallydischarged by five percent or less of a total battery design capacitywithin 24 hours after manufacture). In some embodiments, pre-dischargingcan include discharging the battery at a continuous drain rate or anintermittent drain rate. The freshly assembled battery can be partiallydischarged at a low rate of 5 to 100 mA/g of active material within 24hours after manufacture. In some embodiments, the freshly assembledbattery can be partially discharged at a high rate of 10 to 60 mA/g ofactive material within 24 hours after manufacture. Partially dischargingthe battery can include a step-wise discharge process.

In some embodiments, partially discharging the battery is performed at25° C. (e.g., at a temperature of from 20 to 30° C.).

In some embodiments, the battery includes a cathode comprising an oxidehaving a formula A_(x)Ni_(1-y-z-w)Co_(y)M^(a) _(z)M^(b) _(w)O₂; ananode; a separator between the cathode and the anode; and an alkalineelectrolyte, wherein A is an alkali metal, M^(a) is a metal dopant,M^(b) is a non-metal dopant, 0≦x≦0.2, w is 0, or 0≦w≦0.02 and0.02≦y+z≦0.25.

Embodiments of the battery may include one or more of the followingadvantages.

The battery can have an average closed circuit voltage of less thanabout 1.65 V (e.g., greater than about 1.45 V and/or less than about 1.7V), and can be compatible with devices designed for use withconventional alkaline batteries that include EMD-zinc and nickeloxyhydroxide-zinc. The alkaline battery can have a significantly greatergravimetric specific capacity when compared to commercial primaryalkaline batteries that include EMD-zinc and nickel oxyhydroxide-zinc.For example, the alkaline battery can include greater than about 325mAh/g (e.g., greater than about 350 mAh/g, greater than about 375 mAh/g,greater than about 425 mAh/g, or greater than about 450 mAh/g) whendischarged at relative low rates (e.g., <C/30) to a 0.8 V cutoffvoltage. The battery can have a better high-rate (e.g., >C/3)performance and comparable or greater capacity retention after storageat ambient room temperature and elevated temperatures, when compared tocommercial primary alkaline batteries.

In some embodiments, primary alkaline batteries having cathodes thatinclude a metal-doped Ni(IV)-containing active material can havedecreased internal gas pressure after storage compared to batteries thatinclude an undoped Ni(IV)-containing active material. Metal-doping candecrease generation of oxygen gas from decomposition of alkalineelectrolyte by Ni(IV)-containing active materials during storage atambient room temperature and/or at elevated temperatures.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic side sectional view of an alkaline primary roundcell/battery.

FIG. 2 is a plot depicting the Ni-rich portion of the ternarycomposition diagram for Li—Ni—Co—Mg and Li—Ni—Co—Al oxide systems,indicating the compositions of 26 metal-doped lithium nickel oxides,which are precursors to the corresponding delithiated metal-dopednickel(IV) oxides.

FIG. 3 is a plot depicting an overlay of the x-ray powder diffractionpatterns for cobalt, and cobalt and magnesium-doped lithium nickel oxidecompositions, and undoped lithium nickel oxide, measured using Cu Kαradiation and scanned between 17 and 46 degrees 2θ.

FIG. 4 is a plot depicting an overlay of the x-ray powder diffractionpatterns for cobalt, and cobalt and aluminum-doped lithium nickel oxidecompositions, and undoped lithium nickel oxide, measured using Cu Kαradiation and scanned between 17 and 46 degrees 2θ.

FIG. 5 includes SEM images showing representative morphologies andcrystallite sizes for selected metal-doped lithium nickel oxide powders:(a) undoped lithium nickel oxide, LiNiO₂; (b) magnesium-doped lithiumnickel oxide, LiNi_(0.96)Mg_(0.04)O₂; (c) aluminum-doped lithium nickeloxide, LiNi_(0.96)Al_(0.04)O₂; (d) cobalt and magnesium-doped lithiumnickel oxide, Li(Ni_(0.92)Co_(0.04)Mg_(0.04))O₂; and (e) cobalt-dopedlithium nickel oxide, LiNi_(0.92)Co_(0.08)O₂. Magnification for allcases is 10,000×.

FIG. 6 is a plot depicting an overlay of the voltage profile curves foralkaline button cells with cathodes including delithiated metal-dopednickel (IV) oxides: (a) Li_(x)Ni_(0.88)Co_(0.06)Mg_(0.06)O₂; (b)Li_(x)Ni_(0.88)Co_(0.08)Mg_(0.04)O₂; (c)Li_(x)Ni_(0.88)Co_(0.10)Mg_(0.02)O₂; and (d) Li_(x)Ni_(0.88)Co_(0.12)O₂,discharged at a nominal low rate (i.e., 7.5 mA/g) to a 0.8 V cutoffvoltage.

FIG. 7 is a plot depicting an overlay of the voltage profile curves foralkaline button cells with cathodes including delithiated metal-dopednickel (IV) oxides: (a) Li_(x)Ni_(0.88)Co_(0.04)Al_(0.08)O₂; (b)Li_(x)Ni_(0.88)Co_(0.06)Al_(0.06)O₂; (c)Li_(x)Ni_(0.88)Co_(0.08)Al_(0.04)O₂; and (d)Li_(x)Ni_(0.88)Co_(0.10)Al_(0.02)O₂; and (e) Li_(x)Ni_(0.88)Co_(0.12)O₂discharged at a nominal low rate (i.e., 7.5 mA/g) to a 0.8 V cutoffvoltage.

FIG. 8 is a plot depicting a comparison of discharge capacities foralkaline button cells containing undoped delithiated nickel (IV) oxideand the delithiated metal-doped nickel(IV) oxides that were acid-treatedfor either 40 hours or 20 hours and discharged at a nominal low-rate(i.e., 7.5 mA/g) to a 0.8 V cutoff voltage.

FIG. 9 is a plot depicting a comparison of capacity retention values foralkaline button cells containing delithiated metal-doped nickel (IV)oxides that were acid-treated for either 40 hours or 20 hours, andstored at 45° C. for 1 week before discharge, versus the correspondinginitial OCV values.

FIG. 10 is a plot depicting a comparison of discharge curves foralkaline button cells with cathodes including: (a) delithiated cobaltand aluminum-doped nickel (IV) oxide, (a)Li_(x)Ni_(0.80)Co_(0.15)Al_(0.05)O₂; (b) delithiated cobalt, aluminum,and boron-doped nickel(IV) oxide,Li_(x)Ni_(0.791)Co_(0.149)Al_(0.049)B_(0.01)O₂; (c.) delithiated undopednickel (IV) oxide, Li_(x)NiO₂; and (d.) electrolytic manganese dioxide(EMD), all discharged at a nominal low rate (i.e., 9.5 mA/g) to a 0.8 Vcutoff voltage.

FIG. 11 is a plot depicting a comparison of OCV versus time for alkalinebutton cells with cathodes including delithiated, undoped nickel (IV)oxide that were pre-discharged at a continuous low-rate (i.e., 9.5 mA/g)by (a) 2.5% (upper curve) and (b) 5% (lower curve) of the total designcapacity and held for at least 110 hours at 25° C.

FIG. 12 is a plot depicting a an overlay of the discharge voltageprofile curves for alkaline button cells with cathodes including adelithiated undoped nickel (IV) oxide: (a) stored 24 hours at 25° C.;(b) pre-discharged by 10% of the total design capacity and stored oneweek at 60° C.; (c) stored 1 week at 60° C. and discharged at a nominallow rate (i.e., 9.5 mA/g) to a 0.8 V cutoff voltage.

FIG. 13 includes an overlay of plots depicting a comparison of dischargecurves for alkaline button cells with cathodes including a delithiated,undoped nickel (IV) oxide that were pre-discharged by either (a) 5% or(b) 10% of the total design capacity and discharged at a nominal lowrate (i.e., 7.5 mA/g) to a 0.8 V cutoff voltage after storage for 1, 7,and 14 days at 25° C.; 7 days at 45° C.; and 7 days at 60° C.

FIG. 14 includes overlays of plots depicting a comparison of dischargecurves for alkaline button cells with cathodes including a delithiated,cobalt and magnesium-doped nickel (IV) oxide,Li_(0.07)Ni_(0.92)Co_(0.04)Mg_(0.04)O₂, that were pre-discharged byeither (a) 5% or (b) 10% of the total design capacity and discharged ata nominal low rate (i.e., 7.5 mA/g) to a 0.8 V cutoff voltage afterstorage for 1, 7, and 14 days at 25° C.; 7 days at 45° C.; and 7 days at60° C.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring to FIG. 1, a battery 10 includes a cylindrical housing 18, acathode 12 in the housing, an anode 14 in the housing, and a separator16 between the cathode and the anode. Battery 10 also includes a currentcollector 20, a seal 22, and a metal top cap 24, which serves as thenegative terminal for the battery. Cathode 12 is in contact with housing18, and the positive terminal of battery 10 is at the opposite end ofbattery 10 from the negative terminal. An electrolyte solution, e.g., analkaline solution, is dispersed throughout battery 10.

Cathode 12 can include an electrochemically active material having adoped alkali-deficient nickel oxide that optionally includes protons, anelectrically conductive additive, and optionally a binder.

An undoped alkali-deficient nickel oxide can be an alkali-deficientnickel oxide having a generic formula A_(x)NiO₂, where “A” is an alkalimetal ion, and x is less than 1 (e.g., 0≦x≦0.2). In some embodiments, xis between about 0.06 and 0.07. In some embodiments, x is as small aspossible to maximize an amount of Ni(IV) in a given alkali-deficientnickel oxide. The undoped alkali-deficient nickel oxide can have adeficiency of alkali metals compared to a nominally stoichiometriccompound having a generic formula of ANiO₂. The alkali-deficient nickeloxide can contain defects in the crystal lattice, for example, in thecase where the alkali metal has deintercalated or leached out of thecrystal lattice. In some embodiments, Ni ions can partially occupyalkali metal sites in the crystal lattice. In some embodiments, thealkali metal includes Li, Na, K, Cs, and/or Rb.

In some embodiments, the alkali-deficient nickel oxide can be doped witha dopant metal, such as Co, Mg, Al, Ca, Mn, and/or Y. The metal-dopedalkali-deficient nickel oxide can have a general formula ofA_(x)Ni_(1-y-z)Co_(y)M^(a) _(z)O₂, where A is an alkali metal, M^(a) isa dopant metal such as Mg, Al, Ca, Mn, and/or Y, 0≦x≦0.15, and0.02≦y+z≦0.25. M^(a) can be a single metal or a mixture of metals. Inthe metal-doped alkali-deficient nickel oxide, Co can be present orabsent, and Mg, Al, Ca, Mn, and/or Y can be present or absent; providedthat at least one of Co, or an element selected from Mg, Al, Ca, Mn, andY is present in the alkali-deficient doped nickel oxide. For example,the metal-doped alkali-deficient nickel oxide can have a nominal formulaLi_(0.12)Ni_(0.92)Co_(0.08)O₂. In some embodiments, the metal-dopedalkali-deficient nickel oxide can have a formula ofLi_(x)Ni_(1-y)Co_(y)O₂, Li_(x)Ni_(1-z)Mg_(z)O₂,Li_(x)Ni_(1-y-z)Co_(y)Mg_(z)O₂, Li_(x)Ni_(1-z)Al_(z)O₂,Li_(x)Ni_(1-y-z)Co_(y)Al_(z)O₂, Li_(x)Ni_(1-z)(Mg, Al)_(z)O₂,Li_(x)Ni_(1-y-z)Co_(y)(Mg, Al)_(z)O₂, Li_(x)Ni_(1-z)Ca_(z)O₂,Li_(x)Ni_(1-y-z)Co_(y)Ca_(z)O₂, Li_(x)Ni_(1-z)Y_(z)O₂,Li_(x)Ni_(1-y-z)Co_(y)Y_(z)O₂, Li_(x)Ni_(1-z)Mn_(z)O₂ orLi_(x)Ni_(1-y-z)Co_(y)Mn_(z)O₂. The dopant (e.g., Co, Mg, Al, Ca, Mn,and/or Y) ion can substitute for Ni ions and/or partially substitute forthe alkali ions in the alkali metal sites between the nickel-oxygenlayers in the nickel oxide crystal lattice.

In some embodiments, the alkali-deficient nickel oxide can be doped withboth a non-metal dopant, such as boron (B), silicon (Si) or germanium(Ge), and a metal dopant, such as Co, Mg, Al, Ca, Mn, and/or Y. Themetal and non-metal doped alkali-deficient nickel oxide can have ageneral formula of A_(x)Ni_(1-y-z-w)Co_(y)M^(a) _(z)M^(b) _(w)O₂, whereA is an alkali metal, M^(a) is a metal dopant such as Mg, Al, Ca, Mn,and/or Y, 0≦x≦0.2, and 0.02≦y+z≦0.25, and M^(b) is a non-metal dopantsuch as B, Si, and/or Ge and 0≦w≦0.02. In some embodiments, x<1 and(y+z)<0.2; or x<1, 0.01≦y≦0.2, and 0.01≦z≦0.2. For example, the metaland non-metal doped alkali-deficient nickel oxide can have a nominalformula Li_(0.1)Ni_(0.79)Co_(0.15)Al_(0.05)B_(0.01)O₂.

In some embodiments, in a doped alkali-deficient nickel oxide having aformula of A_(x)Ni_(1-y-z)Co_(y)M^(a) _(z)O₂ orA_(x)Ni_(1-y-z-w)Co_(y)M^(a) _(z)M^(b) _(w)O₂, x is less than or equalto 0.2 (e.g., less than or equal to 0.15, less than or equal to 0.12,less than or equal to 0.1, less than or equal to 0.08, less than orequal to 0.05, or less than or equal to 0.03) and/or greater than orequal to 0 (e.g., greater than or equal to 0.03, greater than or equalto 0.05, greater than or equal 0.08, greater than or equal to 0.1,greater than or equal to 0.12, or greater than or equal to 0.15). Insome embodiments, to enhance discharge performance, x is less than 0.3.In some embodiments, at least one of y or z is greater than 0. As anexample, y+z is greater than 0 (e.g., greater than or equal to 0.02,greater than or equal to 0.04, greater than or equal to 0.08, greaterthan or equal to 0.1, greater than or equal to 0.15, greater than orequal to 0.2, or greater than or equal to 0.22) and/or less than orequal to 0.25 (e.g., less than or equal to 0.22, less than or equal to0.2, less than or equal to 0.15, less than or equal to 0.1, less than orequal to 0.08, less than or equal to 0.04, or less than or equal to0.02). In some embodiments, y is greater than or equal to 0 (e.g.,greater than or equal to 0.02, greater than or equal to 0.04, greaterthan or equal to 0.08, greater than or equal to 0.1, greater than orequal to 0.12) and/or less than or equal to 0.2 (e.g., less than orequal to 0.15, less than or equal to 0.12, less than or equal to 0.1,less than or equal to 0.08, or less than or equal to 0.04). In someembodiments, z is greater than or equal to 0 (e.g., greater than orequal to 0.02, greater than or equal to 0.03, greater than or equal to0.04, greater than or equal to 0.05, greater than or equal to 0.06, orgreater than or equal to 0.07) and/or less than or equal to 0.1 (e.g.,less than or equal to 0.08, less than or equal to 0.07, less than orequal to 0.06, less than or equal to 0.05, less than or equal to 0.04,or less than or equal to 0.03). In some embodiments, w is greater thanor equal to 0 (e.g., greater than or equal to 0.005, greater than orequal to 0.01, or greater than or equal to 0.015) and/or less than orequal to 0.02 (less than or equal to 0.015, less than or equal to 0.01,or less than or equal to 0.005).

In some embodiments, when a doped alkali-deficient nickel oxide hasthree dopants (e.g., two metal dopants and a non-metal dopant, twonon-metal dopants and a metal dopant, three metal dopants, threenon-metal dopants), the ratio for the three dopants can be, for example,1:1:1; 2:1:1; 2:2:1; 3:1:1; 3:2:1; 4:1:1; 4:3:3; 5:1:1; 5:2:1; 5:3:2;5:4:1; or 6:3:1. As an example, a Co:M^(b) ₁:M^(b) ₂ ratio can be 1:1:1;2:1:1; 2:2:1; 3:1:1; 3:2:1; 4:1:1; 4:3:3; 5:1:1; 5:2:1; 5:3:2; 5:4:1; or6:3:1.

The nickel in an alkali-deficient nickel oxide can have multipleoxidation states. For example, the nickel can have an average positiveoxidation state of greater than 3 (e.g., greater than 3.25, greater than3.5, or greater than 3.8) and/or less than or equal to 4 (e.g., lessthan 3.8, less than 3.5, less than 3.25, or less than 3.2). The nickelof the alkali-deficient nickel oxide can have a higher average oxidationstate than the nickel in a corresponding stoichiometric precursor alkalinickel oxide, prior to removal of alkali metal cation A. In someembodiments, the average oxidation state of the nickel in thealkali-deficient nickel oxide can be 0.3 greater (e.g., 0.5 greater, 0.8greater, or 0.9 greater) than the average oxidation state of the nickelin the corresponding stoichiometric precursor alkali nickel oxide.

The alkali-deficient nickel oxide including nickel with an averagepositive oxidation state of greater than 3 can have a layered structure,a spinel-type structure or can include a physical mixture of layered andspinel-type structures, as well as other related crystal structures. Asan example, a lithium deficient nickel oxide Li_(x)NiO₂, prepared bydelithiation of a layered LiNiO₂, can have either a layered structurerelated to that of the layered LiNiO₂ precursor or a spinel-typestructure, depending on the stoichiometry and/or heat treatmentconditions.

In some embodiments, the alkali-deficient nickel oxides can have alayered crystal structure with alkali metal ions located in interlayerlattice sites located between the nickel-oxygen layers. Thealkali-deficient nickel oxides can have defects where alkali metal ionshave been extracted. In some embodiments, the alkali metal ions can bepartially replaced by protons. The interlayer spacing distance can beeither maintained or changed after oxidative de-intercalation of alkalimetal ion, proton intercalation, and/or alkali metal ion/protonion-exchange. In some embodiments, the interlayer spacing can increasedue to substitution by alkali ions having larger ionic radii. Forexample, the interlayer spacing can increase when Li ions aresubstituted by larger potassium (K) ions, anions, and/or watermolecules. In some embodiments, the interlayer spacing inalkali-deficient nickel oxides can increase due to increasedelectrostatic repulsion between the oxygen-containing layers afteralkali removal.

The metal-doped and undoped alkali-deficient nickel oxides can becharacterized by measurement of their x-ray powder diffraction patterns,elemental compositions, and average particle sizes. In some embodiments,crystal lattice parameters of doped or undoped alkali-deficient nickeloxide and corresponding stoichiometric precursors can be determined frompowder X-ray diffraction (“XRD”) patterns. For example, X-ray powderdiffraction patterns can be measured with an X-ray diffractometer (e.g.,Bruker D-8 Advance X-ray diffractometer, Rigaku Miniflex diffractometer)using Cu K_(α), or Cr K_(α) radiation by standard methods described, forexample, by B. D. Cullity and S. R. Stock (Elements of X-rayDiffraction, 3^(rd) ed., New York: Prentice Hall, 2001). The unit cellparameters can be determined by Rietveld refinement of the powderdiffraction data. The X-ray crystallite size also can be determined byanalysis of peak broadening in a powder diffraction pattern of a samplecontaining an internal Si standard using the single-peak Scherrer methodor the Warren-Averbach method as discussed in detail, for example, by H.P. Klug and L. E. Alexander (X-ray Diffraction Procedures forPolycrystalline and Amorphous Materials, New York: Wiley, 1974,618-694). In some embodiments, a layered, metal-doped lithium-deficientnickel oxide, for example, Li_(x)Ni_(1-y-z)Co_(y)M^(a) _(z)O₂ orLi_(x)Ni_(1-y-z-w)Co_(y)M^(a) _(z)M^(b) _(w)O₂ can have an X-raydiffraction pattern indicating that interlayer spacing has changedrelatively little compared to undoped LiNiO₂. For example, the 003Miller index line at the approximate diffraction angle of 2θ=18.79° canremain almost at the same angle while other Miller index (e.g., hk0)lines can show a larger shift, indicating a relatively minor change in aand/or b unit cell parameters axis of the crystal lattice. The extent ofstructural distortion also can depend on the average nickel oxidationstate, the site occupancy of the lithium ions and protons, as well astotal lithium ion/proton content.

In some embodiments, the mean particle size and size distribution for analkali-deficient nickel oxide and the corresponding precursor alkalinickel oxide can be determined with a laser diffraction particle sizeanalyzer (e.g., a SympaTec Helos particle size analyzer equipped with aRodos dry powder dispersing unit) using algorithms based on Fraunhoferor Mie theory to compute the volume distribution of particle sizes andmean particle sizes. Particle size distribution and volume distributioncalculations are described, for example, in M. Puckhaber and S. Rothele(Powder Handling & Processing, 1999, 11(1), 91-95 and European CementMagazine, 2000, 18-21). In some embodiments, the alkali nickel oxideprecursor can include an agglomerate or a sintered aggregate (i.e.,secondary particles) composed of much smaller primary particles. Suchagglomerates and aggregates are readily measured using the particle sizeanalyzer. In some embodiments, scanning electron microscopy (“SEM”) canbe used to determine the morphology and average particle sizes ofparticles of a nickel oxide.

In some embodiments, the content of the nickel, metal dopants, andalkali metals in doped and undoped alkali-deficient nickel oxides can bedetermined by, for example, inductively coupled plasma atomic emissionspectroscopy (“ICP-AE”) and/or atomic absorption spectroscopy (“AA”)using standard methods as described, for example, by J. R. Dean(Practical Inductively Coupled Plasma Spectroscopy, Chichester, England:Wiley, 2005, 65-87) and B. Welz and M. B. Sperling (Atomic AbsorptionSpectrometry, 3^(rd) ed., Weinheim, Germany: Wiley VCH, 1999, 221-294).For example, ICP-AE spectroscopy measurements can be performed using aThermo Electron Corporation IRIS intrepid II XSP ICP with Cetac ASX-510autosampler attachment. For some nickel oxide samples including lithiumand nickel, ICP-AE analysis can be performed separately for Li(λ=670.784 nm), Co (λ=228.616 nm) and Ni (λ=221.647 nm). Analysis ofdoped or undoped alkali-deficient nickel oxide samples for metals can beperformed by a commercial analytical laboratory, for example, GalbraithLaboratories, Inc. (Knoxyille, Tenn.). Proton content can be analyzedusing a type of neutron activation analysis known as PGAA (PromptGamma-ray Activation Analysis) at University of Texas—Austin using thegeneral methods described, for example, by G. L. Molnar (Handbook ofPrompt Gamma Activation Analysis, Dordrecht, The Netherlands: KluwerAcademic Publishers, 2004). The average oxidation state of the nickeland transition metals dopants (e.g., Co, Mn) in the metal-doped lithiumnickel oxides can be determined by chemical titrimetry using ferrousammonium sulfate and standardized potassium permanganate solutions asdescribed, for example, by A. F. Dagget and W. B. Meldrun (QuantitativeAnalysis, Boston: Heath, 1955, 408-9). The average oxidation state ofthe transition metals also can be determined indirectly from thespecific gravimetric capacity observed for coin cells including themetal-doped lithium-deficient nickel oxide as the cathode activematerial, Li metal as the anode active material, and a non-aqueouselectrolyte solution.

Elemental analyses of selected compositions of doped and undoped alkalinickel oxide powders can be performed. Samples can be measured usinginductively coupled plasma atomic emission spectroscopy (“ICP-AE”) by acommercial analytical laboratory (e.g., Galbraith Laboratories, Inc.,Knoxyille, Tenn.).

True densities of an alkali-deficient nickel oxide and the correspondingprecursor nickel oxide can be measured by a He gas pycnometer (e.g.,Quantachrome Ultrapyc Model 1200e) as described in general by P. A. Webb(“Volume and Density Determinations for Particle Technologists”,Internal Report, Micromeritics Instrument Corp., 2001, pp. 8-9) and in,for example, ASTM Standard D5965-02 (“Standard Test Methods for SpecificGravity of Coating Powders”, ASTM International, West Conshohocken, Pa.,2007) and ASTM Standard B923-02 (“Standard Test Method for Metal PowderSkeletal Density by Helium or Nitrogen Pycnometry”, ASTM International,West Conshohocken, Pa., 2008). True density is defined, for example, bythe British Standards Institute, as the mass of a particle divided byits volume, excluding open and closed pores.

Inclusion of a stabilized delithiated nickel oxide containingtetravalent nickel (i.e., Ni(IV)) in a cathode active material cansubstantially improve overall discharge performance of primary alkalinebatteries compared to batteries including conventional cathode activematerials (e.g., electrolytic manganese dioxide (EMD) or β-nickeloxyhydroxide). In some embodiments, alkaline batteries with cathodesincluding Ni(IV)-containing active materials can exhibit an initial or“fresh” (i.e., measured with 1 hour after cell closure) open circuitvoltage (OCV) of greater than about 1.90 V and less than about 2.10 V.Without wishing to be bound by theory, it is believed that alkalinebatteries with cathodes including Ni(IV)-containing active materialshaving a lower OCV (e.g., less than about 1.75 V, less than about 1.70V) can be advantageous for use with certain battery-powered electronicdevices, such as devices designed for use with standard commercialalkaline batteries. In some embodiments, alkaline batteries withcathodes including Ni(IV)-containing active materials can have adequatecapacity retention after storage for longer than about 1-2 weeks atambient room temperature (e.g., or at elevated temperatures such as 45°C. or 60° C.) for extended periods of time (e.g., for one week orlonger, two weeks or longer, three weeks or longer), which can providebatteries with a useful shelf life.

In some embodiments, freshly assembled (i.e., within about 1 hour afterclosure) cells can have an average open circuit voltage (OCV) of about1.85 V or greater. In other embodiments, the freshly assembled cells canhave a closed circuit voltage (CCV) of less than about 1.8 V (e.g., lessthan about 1.7 V, or less than about 1.6 V). Freshly assembled cells canhave a significantly greater gravimetric specific capacity, for example,greater than about 350 mAh/g (e.g., greater than about 375 mAh/g,greater than about 425 mAh/g, or greater than about 450 mAh/g) whendischarged at relatively low drain rates (e.g., <C/30 or <C/40) to a 0.8V cutoff voltage than commercial primary alkaline batteries (e.g.,manganese dioxide (EMD)/zinc, or nickel oxyhydroxide/zinc batteries).

In some embodiments, the metal-doped alkali-deficient nickel oxide has anominal low rate capacity of at least 350 mAh/g (e.g., at least 375mAh/g) and a high-rate capacity of at least 370 mAh/g (e.g., at least385 mAh/g) when discharged after storing for 24 hours at 25° C. Themetal-doped alkali-deficient nickel oxide can have a low rate capacityof at least 340 mAh/g (e.g., at least 350 mAh/g, at least 360 mAh/g)after storing for one week at 25° C. The metal-doped alkali-deficientnickel oxide can have a nominal low rate capacity of at least 300 mAh/g(e.g., at least 310 mAh/g, at least 315 mAh/g, at least 320 mAh/g, atleast 325 mAh/g) after storing for one week at 45° C.

In some embodiments, alkaline cells with cathodes including themetal-doped alkali-deficient nickel oxide have a capacity retention ofat least 90 percent (e.g., at least 95%) when discharged at a nominallylow rate after storing for one week at 25° C. Alkaline cells withcathodes including the metal-doped alkali-deficient nickel oxide canhave a capacity retention of at least 80 percent (e.g., at least 85percent) when discharged at a nominally low rate after storing for oneweek at 45° C.

In some embodiments, alkaline batteries with cathodes including ametal-doped alkali-deficient nickel oxide can have decreased internalgas pressure buildup during storage. Without wishing to be bound bytheory, it is believed that the gradual buildup of gas pressure duringstorage can result from generation of oxygen gas due to degradation ofthe alkaline electrolyte, via oxidation of water by nickel (IV) at highOCV, as shown in Equation 1.

Li_(x)Ni(IV)_(1-x)Ni(III)_(x)O₂+H₂O→NiII)(OH)₂ +xLi⁺+½O₂  (1)

An increase in the internal gas pressure of a cell can be undesirable,as product safety can be compromised for the consumer. For example, anincrease in internal pressure can cause the battery to leak and/or ventif the gas pressure becomes sufficiently high. In some embodiments,decreasing the initial OCV of alkaline primary batteries having cathodesincluding metal-doped alkali-deficient nickel oxide cathode activematerials can decrease the overall rate of oxygen generation, resultingin less gas pressure buildup during long term storage.

In some embodiments, the metal-doped alkali-deficient nickel oxidepowder has a cumulative oxygen evolution volume after storing for threeweeks at 25° C. in alkaline electrolyte solution of less than 5 cm³/g(e.g., less than 6 cm³/g, less than 7 cm³/g). In some embodiments, thecorresponding value for undoped alkali-deficient nickel oxide powder isgreater than 8.5 cm³/g.

In general, an alkali-deficient nickel oxide can be prepared bytreatment of a layered lithium nickel oxide precursor having a nominalstoichiometric formula of LiNiO₂ with a 2-12 M aqueous solution of astrong mineral acid (e.g., sulfuric acid, nitric acid, hydrochloricacid) at a temperature below ambient room temperature (e.g., betweenabout 0 and 5° C.) for various periods of times ranging between 20 and60 hours. Nearly all the lithium ions can be extracted from theinterlayer regions between the Ni-oxygen layers in the crystal lattice.A suitable layered lithium nickel oxide precursor having specificphysicochemical properties can be synthesized from a commercialspherical nickel hydroxide by any of several methods including both highand low temperature processes. For example, a layered lithium nickeloxide precursor can be synthesized by procedures described by Ohzuku andco-workers (J. Electrochem. Soc., 1993, 140, 1862); Ebner and co-workers(Solid State Ionics, 1994, 69, 238); U.S. Pat. Nos. 4,980,080;5,180,574; 5,629,110; and 5,264,201, each herein incorporated byreference in its entirety. A layered lithium nickel oxide precursorhaving at least a portion of the Ni ions substituted by one or moreother metal or non-metal ions can be prepared, for example, via a solidstate reaction of a mixture of suitable metal-containing precursorpowders, as described, for example, in U.S. Pat. No. 4,980,080, U.S.Pat. No. 5,629,110, U.S. Pat. No. 5,955,051, U.S. Pat. No. 5,720,932,U.S. Pat. No. 6,274,270, and U.S. Pat. No. 6,335,119, each hereinincorporated by reference in its entirety. The metal ions can betransition metal ions (e.g., Co, Mn, Y), alkaline earth metal ions(e.g., Ca, Mg), or main group metal ions (e.g., Al). Non-metal ions(e.g., B, Si, Ge) also can be substituted for Ni ions and/or Li ions.

In some embodiments, to prepare an undoped lithium nickel oxide, anundoped f3-nickel oxyhydroxide can be mixed with a stoichiometric amount(i.e., 1:1) of lithium hydroxide monohydrate (LiOH.H₂O) using a highenergy milling process (e.g., a high-energy shaker mill, a planetarymill, a stirred ball mill, a small media mill). The mixture can beheated sequentially at two different treatment temperatures in flowingoxygen gas. For example, initially, the mixture can be heated to about210° C. (about 0.5° C./min), held for at temperature for 16-20 hours,and then allowed to furnace cool (in an oxygen flow) to ambient roomtemperature. Next, the mixture can be re-milled, heated to about 800° C.(0.5° C./min) with, for example, two intermediate temperature soaks(i.e., at about 105° C. for 30 minutes; at about 350° C. for 3 hours),held at about 800° C. for 48 hours, and finally allowed to furnace coolto ambient room temperature.

In some embodiments, to prepare the multi-metal-doped lithium nickeloxide, an undoped β-nickel oxyhydroxide powder and selected metal ionsources, for example, aluminum metal powder, aluminum hydroxide (e.g.,Al(OH)₃), cobalt oxide (e.g., Co₃O₄), cobalt carbonate (CoCO₃),magnesium oxide (MgO), calcium oxide (CaO), calcium hydroxide (Ca(OH)₂),calcium carbonate (CaCO₃), yttrium hydroxide (Y(OH)₃), manganese oxide(e.g., MnO, Mn₂O₃, MnO₂), manganese carbonate (MnCO₃), and/or lithiumhydroxide monohydrate in specified stoichiometric ratios can be mixed bya high-energy milling process. The stoichiometries of the compositionscan be selected according to composition diagrams corresponding toselected ternary lithium metal-dopant nickel oxide systems, for example,LiNi_(1-y-z)Co_(y)Mg_(z)O₂ and LiNi_(1-y-z)Co_(y)Al_(z)O₂. Thehigh-energy milled mixtures including nickel oxyhydroxide and variousmetal ion sources serving as precursors to the metal-doped lithiumnickel oxides can be heated as above for the undoped lithium nickeloxide.

In some embodiments, at least a portion of the Ni ions in a layeredlithium nickel oxide precursor can substituted by one or more non-metalions (e.g., B, Si, Ge). A mixed metal and nonmetal-doped lithium nickeloxide can be prepared by blending an undoped β-nickel oxyhydroxidepowder, selected metal sources, and selected nonmetal sources, forexample, boron oxide (B₂O₃), silicon powder (Si), silicon dioxide(SiO₂), germanium powder (Ge), germanium dioxide (GeO₂) and/or lithiumhydroxide monohydrate in specified stoichiometric ratios and thoroughlymixing by a high-energy milling process. The high-energy milled mixturesincluding the nickel oxyhydroxide and the various nonmetal and metalsources serving as precursors to the mixed nonmetal and metal-dopedlithium nickel oxides can be heated as above for the metal-doped lithiumnickel oxides.

In some embodiments, the doped alkali nickel oxides can be prepared viaa modified solid-state process. For example, the nickel source materialcan be a commercial spherical β-nickel oxyhydroxide powder that iseither undoped, or where the nickel is partially substituted by about2-3 atomic % cobalt. The β-nickel oxyhydroxide can be prepared bychemical oxidation of β-nickel hydroxide as follows. An excess of solidsodium peroxydisulfate Na₂S₂O₈ can be added in portions to a stirredslurry of a commercial spherical cobalt-substituted (or unsubstituted)β-nickel hydroxide powder in de-ionized water at about 30-40° C. Themixture can then be heated to about 50-60° C. and stirred for about 15hours with incremental addition of portions of aqueous NaOH solution orsolid powder to maintain pH in the range of 8<pH<12 (e.g., at about 10).Next, the stirring and heating can be stopped and the resultingsuspension of black particles can be allowed to settle (e.g., 1-4hours). A clear supernatant liquid can be removed and the particles canbe re-suspended in a fresh aliquot of water (e.g., de-ionized water).This suspension can be stirred for 5-30 minutes, allowed to settle, thesupernatant removed, and the entire process can be repeated until the pHof the supernatant is nearly neutral (e.g., 6<pH<8, or about 7). Thewashed β-nickel oxyhydroxide solid product can be dried in air at about80-100° C.

In some embodiments, preparation of Ni(IV)-containing cathode activematerials requires removal of most of the interlayer Li ions from thelayered lithium nickel oxide precursors. In some embodiments, the Liions are chemically extracted via an oxidative delithiation process.Oxidative delithiation of a layered lithium nickel oxide can take placevia a proton catalyzed aqueous disproportionation process such as thatdescribed in Equation 2 and as reported by H. Arai and coworkers (J.Solid State Chem., 2002, 163, 340-9). For example, treatment of alayered lithium nickel oxide powder with an aqueous 6M H₂SO₄ solution atvery low pH can cause Ni(III) ions on the surfaces of the particles todisproportionate into equal numbers of Ni(II) and Ni(IV) ions.

2LiNi⁺³O₂+4H⁺→Ni⁺⁴O₂+Ni⁺²+2Li⁺+2H₂O  (2)

The Ni(II) ions can dissolve in the acid solution whereas the Ni(IV)ions are insoluble and can remain in the solid phase.

In some embodiments, ionic exchange of Li ions by protons can take placevia hydrolysis such as described in Equation 3. However, theintroduction of protons into lattice sites formerly occupied by Li ionsin the interlayer region can be undesirable since these protons canremain in the lattice even after acid treatment, and inhibit thedisproportionation reaction. Further, these protons can interfere withsolid state diffusion of protons inserted during discharge of cellsincluding the lithium deficient nickel oxide as active cathode materialas well as limit total discharge capacity.

LiNi⁺³O₂+H₂O→H_(x)Li_((1-x))Ni⁺³O₂ +xLiOH  (3)

An improved process for oxidative delithiation of metal-substitutedlayered lithium nickel oxides by treatment with an aqueous solution of amineral acid at a relatively low temperature (e.g., between 0° C. and 5°C.) was described, for example, in U.S. application Ser. No. 12/722,669.After treatment by the low-temperature acid washing process in U.S.application Ser. No. 12/722,669, the isolated solid product can exhibita total weight loss of about 50% relative to the initial dry weight ofthe corresponding metal-substituted LiNi_(1-y-z)Co_(y)M_(z)O₂ phase.This weight loss can be attributed to, for example, the partialdissolution of Ni(II) ions as well as the extraction of Li⁺ ions.Dissolution of Ni⁺² ions from the surface of the lithium nickel oxideparticles can increase particle porosity thereby increasing exposure ofNi⁺³ ions inside the particles to acid and resulting additionaldisproportionation. An increase in the amount of disproportionation canserve to raise the average Ni oxidation state. In some embodiments, thealkali-deficient nickel oxide is prepared as described, for example, inU.S. Application U.S. Ser. No. 12/722,669, herein incorporated byreference in its entirety.

In some embodiments, the alkali-deficient nickel oxide includes protons.For example, the alkali-deficient nickel oxide can include protons at astoichiometric ratio of between 0.01 and 0.2 atomic percent.

X-ray powder diffraction patterns of selected compositions ofdelithiated metal substituted nickel oxide powders can be measured inthe same manner as the corresponding metal substituted lithium nickeloxides. The observed patterns can be consistent with those reportedpreviously, for example, by H. Arai et al. (e.g., J. Solid State Chem.,2002, 163, 340-9) and also L. Croguennec et al. (e.g., J. Mater. Chem.,2001, 11, 131-41) for other chemically delithiated layered nickel oxideshaving various compositions. The experimental patterns can be consistentwith that reported by T. Ohzuku et al. (e.g., J. Electrochem. Soc.,1993, 140, 1862) for a comparable sample of delithiated nickel oxide.

The alkali-deficient nickel oxide resulting from repeated acid treatmentcan have greater purity, greater B.E.T. specific surface area, and/orlarger average pore diameter relative to the alkali metal-containingprecursor nickel oxide. The specific surface areas of analkali-deficient nickel oxide and the corresponding precursor nickeloxide can be determined by the multipoint B.E.T. N₂ adsorption isothermmethod described, for example, by P. W. Atkins (Physical Chemistry,5^(th) edn., New York: W. H. Freeman & Co., 1994, pp. 990-992) and S.Lowell et al. (Characterization of Porous Solids and Powders: PowderSurface Area and Porosity, Dordrecht, The Netherlands: Springer, 2006,pp. 58-80). The B.E.T. surface area method measures the total surfacearea on the exterior surfaces of particles and includes that portion ofthe surface area defined by open pores within the particle accessiblefor gas adsorption and desorption. In some embodiments, the specificsurface area of the alkali-deficient nickel oxide can be substantiallygreater than that of the precursor nickel oxide. An increase in specificsurface area can be correlated with an increase in surface roughness andporosity, which also can be assessed by analyzing the microstructure ofthe nickel oxide particles as imaged by scanning electron microscopy(e.g., SEM micrographs at about 10,000× magnification). Porosimetricmeasurements can be performed on the nickel oxide powders to determinecumulative pore volumes, average pore sizes (i.e., diameters), and poresize distributions. Pore sizes and pore size distributions can becalculated by applying various models and computational methods (e.g.,BJH, DH, DR, HK, SF, etc.) to analyze the data from the measurement ofN₂ adsorption and/or desorption isotherms, as discussed, for example, byS. Lowell et al. (Characterization of Porous Solids and Powders: PowderSurface Area and Porosity, Dordrecht, The Netherlands: Springer, 2006,pp. 101-156).

In some embodiments, cathode 12 can include between 50 percent and 95percent by weight (e.g., between 60 percent and 90 percent by weight,between 70 percent and 85 percent by weight) of the cathode activematerial. Cathode 12 can include greater than or equal to 50, 60, 70,80, or 90 percent by weight, and/or less than or equal to 95, 90, 80,70, or 60 percent by weight of the cathode active material. Cathode 12can include one or more (e.g., two, three or more) doped and/or undopedalkali-deficient nickel oxides, in any combination. For example, cathode12 can include a mixture of Li_(x)Ni_(1-y)Co_(y)O₂,Li_(x)Ni_(1-y-z)Co_(y)M^(a) _(z)O₂, Li_(x)Ni_(1-y-z-w)Co_(y)M^(a)_(z)M^(b) _(w)O₂, and/or Li_(x)NiO₂, where M^(a) is Ca, Mg, Al, Y and/orMn.

One or more alkali-deficient nickel oxides can make up all of the activematerial of cathode 12, or a portion of the active material of cathode12. In a cathode including a mixture or blend of active materials, theactive materials can include greater than about one percent to less thanabout 100 percent by weight of the alkali-deficient nickel oxide. Forexample, cathode 12 can include greater than 0%, 1%, 5%, 10%, 20%, 50%,or 70% by weight of the alkali-deficient nickel oxide (s); and/or lessthan or equal to about 100%, 70%, 50%, 20%, 10%, 5%, or 1% by weight ofthe alkali-deficient nickel oxide(s). Other examples of suitable cathodeactive materials that can be used in combination with thealkali-deficient nickel oxide(s) can be selected from γ-MnO₂ (e.g., EMD,CMD), β-NiOOH, γ-NiOOH, AgO, Ag₂O, AgNiO₂, AgCoO₂, AgCo_(x)Ni_(1-x)O₂,AgCuO₂, Ag₂Cu₂O₃, and combinations thereof.

In some embodiments, cathode 12 can include an electrically conductiveadditive capable of enhancing the bulk electrical conductivity ofcathode 12. Examples of conductive additives include graphite, carbonblack, silver powder, gold powder, nickel powder, carbon fibers, carbonnanofibers, carbon nanotubes, acetylene black, manganese dioxide, cobaltoxide, cobalt oxyhydroxide, silver oxide, silver nickel oxide, nickeloxyhydroxide, and indium oxide. Preferred conductive additives includegraphite particles, graphitized carbon black particles, carbonnanofibers, vapor phase grown carbon fibers, and single and multiwallcarbon nanotubes. In certain embodiments, the graphite particles can benon-synthetic (i.e., “natural”), nonexpanded graphite particles, forexample, NdG MP-0702X available from Nacional de Grafite (Itapecirica,Brazil) and Formula BT™ grade available from Superior Graphite Co.(Chicago, Ill.). In other embodiments, the graphite particles can beexpanded natural or synthetic graphite particles, for example, Timrex®BNB90 available from Timcal, Ltd. (Bodio, Switzerland), WH20 or WH20Agrade from Chuetsu Graphite Works Co., Ltd. (Osaka, Japan), and ABGgrade available from Superior Graphite Co. (Chicago, Ill.). In yet otherembodiments, the graphite particles can be synthetic, non-expandedgraphite particles, for example, Timrex® KS4, KS6, KS15, MX15 availablefrom Timcal, Ltd. (Bodio, Switzerland). The graphite particles can beoxidation-resistant synthetic, non-expanded graphite particles. The term“oxidation resistant graphite” as used herein refers to a syntheticgraphite made from high purity carbon or carbonaceous materials having ahighly crystalline structure. Suitable oxidation resistant graphitesinclude, for example, SFG4, SFG6, SFG10, SFG15 available from Timcal,Ltd., (Bodio, Switzerland). The use of oxidation resistant graphite inblends with another strongly oxidizing cathode active material, nickeloxyhydroxide, is disclosed in commonly assigned U.S. Ser. No.11/820,781, filed Jun. 20, 2007. Carbon nanofibers are described, forexample, in commonly-assigned U.S. Pat. No. 6,858,349 and U.S. PatentApplication Publication No. US 2002-0172867A1. Cathode 12 can includebetween 3% and 35%, between 4% and 20%, between 5% and 10%, or between6% and 8% by weight of conductive additive.

An optional binder can be added to cathode 12 to enhance structuralintegrity. Examples of binders include polymers such as polyethylenepowders, polypropylene powders, polyacrylamides, and variousfluorocarbon resins, for example polyvinylidene difluoride (PVDF) andpolytetrafluoroethylene (PTFE). An example of a suitable polyethylenebinder is available from Dupont Polymer Powders (Sàri, Switzerland)under the tradename Coathylene HX1681. The cathode 12 can include, forexample, from 0.05% to 5% or from 0.1% to 2% by weight binder relativeto the total weight of the cathode. Cathode 12 can also include otheroptional additives.

The electrolyte solution also is dispersed throughout cathode 12, e.g.,at about 5-7 percent by weight. Weight percentages provided above andbelow are determined after the electrolyte solution was dispersed incathode 12. The electrolyte solution can be any of the electrolytesolutions commonly used in alkaline batteries. The electrolyte solutioncan be an alkaline solution, such as an aqueous alkali metal hydroxidesolution, e.g., LiOH, NaOH, KOH, or mixtures of alkali metal hydroxidesolutions (e.g., KOH and NaOH, KOH and LiOH). For example, the aqueousalkali metal hydroxide solution can include between about 33 and about45 percent by weight of the alkali metal hydroxide, such as about 9 NKOH (i.e., about 37% by weight KOH). In some embodiments, theelectrolyte solution also can include up to about 6 percent by weightzinc oxide, e.g., about 2 percent by weight zinc oxide.

Anode 14 can be formed of any of the zinc-based materials conventionallyused in alkaline battery zinc anodes. For example, anode 14 can be agelled zinc anode that includes zinc metal particles and/or zinc alloyparticles, a gelling agent, and minor amounts of additives, such as agassing inhibitor. A portion of the electrolyte solution can bedispersed throughout the anode. The zinc particles can be any of thezinc-based particles conventionally used in gelled zinc anodes. Thezinc-based particles can be formed of a zinc-based material, forexample, zinc or a zinc alloy. Generally, a zinc-based particle formedof a zinc-alloy is greater than 75% zinc by weight, generally greaterthan 99.9% by weight zinc. The zinc alloy can include zinc (Zn) and atleast one of the following elements: indium (In), bismuth (Bi), aluminum(Al), calcium (Ca), gallium (Ga), lithium (Li), magnesium (Mg), and tin(Sn). The zinc alloy generally is composed primarily of zinc andpreferably can include metals that can inhibit gassing, such as indium,bismuth, aluminum and mixtures thereof. As used herein, gassing refersto the evolution of hydrogen gas resulting from a reaction of zinc metalor zinc alloy with the electrolyte. The presence of hydrogen gas insidea sealed battery is undesirable because a pressure buildup can causeleakage of electrolyte. Preferred zinc-based particles are bothessentially mercury-free and lead-free. Examples of zinc-based particlesinclude those described in U.S. Pat. Nos. 6,284,410; 6,472,103;6,521,378; and commonly-assigned U.S. application Ser. No. 11/001,693,filed Dec. 1, 2004, all hereby incorporated by reference. The terms“zinc”, “zinc powder”, or “zinc-based particle” as used herein shall beunderstood to include zinc alloy powder having a high relativeconcentration of zinc and as such functions electrochemicallyessentially as pure zinc. The anode can include, for example, betweenabout 60% and about 80%, between about 62% and 75%, between about 63%and about 72%, or between about 67% and about 71% by weight ofzinc-based particles. For example, the anode can include less than about72%, about 70%, about 68%, about 64%, or about 60%, by weight zinc-basedparticles.

The zinc-based particles can be formed by various spun or air blownprocesses. The zinc-based particles can be spherical or non-spherical inshape. Non-spherical particles can be acicular in shape (i.e., having alength along a major axis at least two times a length along a minoraxis) or flake-like in shape (i.e., having a thickness not more than 20%of the length of the maximum linear dimension). The surfaces of thezinc-based particles can be smooth or rough. As used herein, a“zinc-based particle” refers to a single or primary particle of azinc-based material rather than an agglomeration or aggregation of morethan one particle. A percentage of the zinc-based particles can be zincfines. As used herein, zinc fines include zinc-based particles smallenough to pass through a sieve of 200 mesh size (i.e., a sieve having aTyler standard mesh size corresponding to a U.S. Standard sieve havingsquare openings of 0.075 mm on a side) during a normal sieving operation(i.e., with the sieve shaken manually). Zinc fines capable of passingthrough a 200 mesh sieve can have a mean average particle size fromabout 1 to 75 microns, for example, about 75 microns. The percentage ofzinc fines (i.e., −200 mesh) can make up about 10 percent, 25 percent,50 percent, 75 percent, 80 percent, 90 percent, 95 percent, 99 percentor 100 percent by weight of the total zinc-based particles. A percentageof the zinc-based particles can be zinc dust small enough to passthrough a 325 mesh size sieve (i.e., a sieve having a Tyler standardmesh size corresponding to a U.S. Standard sieve having square openingsof 0.045 mm on a side) during a normal sieving operation. Zinc dustcapable of passing through a 325 mesh sieve can have a mean averageparticle size from about 1 to 35 microns (for example, about 35microns). The percentage of zinc dust can make up about 10 percent, 25percent, 50 percent, 75 percent, 80 percent, 90 percent, 95 percent, 99percent or 100 percent by weight of the total zinc-based particles. Evenvery small amounts of zinc fines, for example, at least about 5 weightpercent, or at least about 1 weight percent of the total zinc-basedparticles can have a beneficial effect on anode performance. The totalzinc-based particles in the anode can consist of only zinc fines, of nozinc fines, or mixtures of zinc fines and dust (e.g., from about 35 toabout 75 weight percent) along with larger size (e.g., −20 to +200 mesh)zinc-based particles. A mixture of zinc-based particles can provide goodoverall performance with respect to rate capability of the anode for abroad spectrum of discharge rate requirements as well as provide goodstorage characteristics. To improve performance at high discharge ratesafter storage, a substantial percentage of zinc fines and/or zinc dustcan be included in the anode.

Anode 14 can include gelling agents, for example, a high molecularweight polymer that can provide a network to suspend the zinc particlesin the electrolyte. Examples of gelling agents include polyacrylicacids, grafted starch materials, salts of polyacrylic acids,polyacrylates, carboxymethylcellulose, a salt of acarboxymethylcellulose (e.g., sodium carboxymethylcellulose) orcombinations thereof. Examples of polyacrylic acids include Carbopol 940and 934 available from B.F. Goodrich Corp. and Polygel 4P available from3V. An example of a grafted starch material is Waterlock A221 or A220available from Grain Processing Corp. (Muscatine, Iowa). An example of asalt of a polyacrylic acid is Alcosorb G1 available from CibaSpecialties. The anode can include, for example, between about 0.05% and2% by weight or between about 0.1% and 1% by weight of the gelling agentby weight.

Gassing inhibitors can include a metal, such as bismuth, tin, indium,aluminum or a mixture or alloys thereof. A gassing inhibitor also caninclude an inorganic compound, such as a metal salt, for example, anindium or bismuth salt (e.g., indium sulfate, indium chloride, bismuthnitrate). Alternatively, gassing inhibitors can be organic compounds,such as phosphate esters, ionic surfactants or nonionic surfactants.Examples of ionic surfactants are disclosed in, for example, U.S. Pat.No. 4,777,100, which is hereby incorporated by reference.

Separator 16 can have any of the conventional designs for primaryalkaline battery separators. In some embodiments, separator 16 can beformed of two layers of a non-woven, non-membrane material with onelayer being disposed along a surface of the other. To minimize thevolume of separator 16 while providing an efficient battery, each layerof non-woven, non-membrane material can have a basic weight of about 54grams per square meter, a thickness of about 5.4 mils when dry and athickness of about 10 mils when wet. In these embodiments, the separatorpreferably does not include a layer of membrane material or a layer ofadhesive between the non-woven, non-membrane layers. Generally, thelayers can be substantially devoid of fillers, such as inorganicparticles. In some embodiments, the separator can include inorganicparticles. In other embodiments, separator 16 can include a layer ofcellophane combined with a layer of non-woven material. The separatoroptionally can include an additional layer of non-woven material. Thecellophane layer can be adjacent to cathode 12. Preferably, thenon-woven material can contain from about 78% to 82% by weightpolyvinylalcohol (PVA) and from about 18% to 22% by weight rayon and atrace amount of surfactant. Such non-woven materials are available fromPDM under the tradename PA25. An example of a separator including alayer of cellophane laminated to one or more layers of a non-wovenmaterial is Duralam DT225 available from Duracell Inc. (Aarschot,Belgium).

In yet other embodiments, separator 16 can be an ion-selectiveseparator. An ion-selective separator can include a microporous membranewith an ion-selective polymeric coating. In some cases, such as inrechargeable alkaline manganese dioxide cells, diffusion of solublezincate ion, i.e., [Zn(OH)₄]²⁻, from the anode to the cathode caninterfere with the reduction and oxidation of manganese dioxide, therebyresulting in a loss of coulombic efficiency and ultimately in decreasedcycle life. Separators that can selectively inhibit the passage ofzincate ions, while allowing free passage of hydroxide ions aredescribed in U.S. Pat. Nos. 5,798,180 and 5,910,366. An example of aseparator includes a polymeric substrate having a wettable celluloseacetate-coated polypropylene microporous membrane (e.g., Celgard® 3559,Celgard® 5550, Celgard® 2500, and the like) and an ion-selective coatingapplied to at least one surface of the substrate. Suitable ion-selectivecoatings include polyaromatic ethers (such as a sulfonated derivative ofpoly(2,6-dimethyl-1,4-phenyleneoxide)) having a finite number ofrecurring monomeric phenylene units each of which can be substitutedwith one or more lower alkyl or phenyl groups and a sulfonic acid orcarboxylic acid group. In addition to preventing migration of zincateions to the manganese dioxide cathode, the selective separator wasdescribed in U.S. Pat. Nos. 5,798,180 and 5,910,366 as capable ofdiminishing diffusion of soluble ionic species away from the cathodeduring discharge

Alternatively or in addition, the separator can prevent substantialdiffusion of soluble ionic metal species (e.g., Ag⁺, Ag²⁺, Cu⁺, Cu²⁺,Bi⁵⁺, and/or Bi³⁺) away from the cathode to the zinc anode, such as theseparator described in U.S. Pat. No. 5,952,124. The separator caninclude a substrate membrane such as cellophane, nylon (e.g., Pellon®sold by Freundenburg, Inc.), microporous polypropylene (e.g., Celgard®3559 sold by Celgard, Inc.) or a composite material including adispersion of a carboxylic ion-exchange material in a microporousacrylic copolymer (e.g., PD2193 sold by Pall-RAI, Inc.). The separatorcan further include a polymeric coating thereon including a sulfonatedpolyaromatic ether, as described in U.S. Pat. Nos. 5,798,180; 5,910,366;and 5,952,124.

In other embodiments, separator 16 can include an adsorptive or trappinglayer. Such a layer can include inorganic particles that can form aninsoluble compound or an insoluble complex with soluble transition metalspecies to limit diffusion of the soluble transition metal speciesthrough the separator to the anode. The inorganic particles can includemetal oxide nanoparticles, for example, as ZrO₂ and TiO₂. Although suchan adsorptive separator can attenuate the concentration of the solubletransition metal species, it may become saturated and lose effectivenesswhen high concentrations of soluble metal species are adsorbed. Anexample of such an adsorptive separator is disclosed in commonlyassigned U.S. Pat. Nos. 7,914,920 and 8,048,556.

Battery housing 18 can be any conventional housing commonly used forprimary alkaline batteries. The battery housing 18 can be fabricatedfrom metal, for example, nickel-plated cold-rolled steel. The housinggenerally includes an inner electrically-conductive metal wall and anouter electrically non-conductive material such as heat shrinkableplastic. An additional layer of conductive material can be disposedbetween the inner wall of the battery housing 18 and cathode 12. Thislayer may be disposed along the inner surface of the wall, along thecircumference of cathode 12 or both. This conductive layer can beapplied to the inner wall of the battery, for example, as a paint ordispersion including a carbonaceous material, a polymeric binder, andone or more solvents. The carbonaceous material can be carbon particles,for example, carbon black, partially graphitized carbon black orgraphite particles. Such materials include LB1000 (Timcal, Ltd.),Eccocoat 257 (W. R. Grace & Co.), Electrodag 109 (Acheson Colloids,Co.), Electrodag 112 (Acheson), and EB0005 (Acheson). Methods ofapplying the conductive layer are disclosed in, for example, CanadianPatent No. 1,263,697, which is hereby incorporated by reference.

The anode current collector 20 passes through seal 22 extending intoanode 14. Current collector 20 is made from a suitable metal, such asbrass or brass-plated steel. The upper end of current collector 20electrically contacts the negative top cap 24. Seal 22 can be made, forexample, of nylon.

Battery 10 can be assembled using conventional methods and hermeticallysealed by a mechanical crimping process. In some embodiments, positiveelectrode 12 can be formed by a pack and drill method, described in U.S.Ser. No. 09/645,632, filed Aug. 24, 2000.

Battery 10 is pre-discharged by discharging less than or equal to 10%(e.g., less than or equal to nine percent, less than or equal to eightpercent, less than or equal to 7.5 percent, less than or equal to sixpercent, less than or equal to five percent, less than or equal to fourpercent, less than or equal to three percent, less than or equal to twopercent, or less than or equal to one percent) of the total designcapacity of the battery within about 1 hour (e.g., 0.75 hour, 1 hour,1.5 hours, 2 hours) after assembly is completed. In some embodiments,pre-discharge can occur on a cathode prior to incorporation into abattery. The battery can be pre-discharged at constant drain ratesranging from less than 7.5 mA/g (i.e., of active material) to more than60 mA/g (e.g., 5 mA/g to 100 mA/g). The current drain duringpre-discharge can be either constant or intermittent (i.e., pulsed) innature, or a combination thereof. The pre-discharge can be performedcontinuously or in discrete steps and can also include one or more restintervals during which no discharge takes place. The pre-discharge canbe performed completely or in part at ambient temperature (e.g., 20-30°C.) as well as at elevated temperatures (e.g., 40-70° C.).

Battery 10 can be a primary electrochemical cell or in some embodiments,a secondary electrochemical cell. Primary batteries are meant to bedischarged (e.g., to exhaustion) only once, and then discarded. In otherwords, primary batteries are not intended to be recharged. Primarybatteries are described, for example, by D. Linden and T. B. Reddy(Handbook of Batteries, 3^(rd) ed., New York: McGraw-Hill Co., Inc.,2002). In contrast, secondary batteries can be recharged many times(e.g., more than fifty times, more than a hundred times, more than athousand times). In some cases, secondary batteries can includerelatively robust separators, such as those having many layers and/orthat are relatively thick. Secondary batteries can also be designed toaccommodate changes, such as swelling, that can occur in the batteries.Secondary batteries are described, for example, by T. R. Crompton(Battery Reference Book, 3^(rd) ed., Oxford: Reed Educational andProfessional Publishing, Ltd., 2000) and D. Linden and T. B. Reddy(Handbook of Batteries, 3^(rd) ed., New York: McGraw-Hill Co., Inc.,2002).

Battery 10 can have any of a number of different nominal dischargevoltages (e.g., 1.2 V, 1.5 V, 1.65 V), and/or can be, for example, a AA,AAA, AAAA, C, or D battery. While battery 10 can be cylindrical, in someembodiments, battery 10 can be non-cylindrical. For example, battery 10can be a coin cell, a button cell, a wafer cell, or a racetrack-shapedcell. In some embodiments, a battery can be prismatic. In certainembodiments, a battery can have a rigid laminar cell configuration or aflexible pouch, envelope or bag cell configuration. In some embodiments,a battery can have a spirally wound configuration, or a flat plateconfiguration. Batteries are described, for example, in U.S. Pat. No.6,783,893; U.S. Patent Application Publication No. 2007/0248879 A1,filed on Jun. 20, 2007; and U.S. Pat. No. 7,435,395.

The following examples are illustrative and not intended to be limiting.

EXAMPLES Example 1 Synthesis of LiNiO₂

A stoichiometric lithium nickel oxide, LiNiO₂ was synthesized byblending 93.91 g of a commercial spherical β-nickel oxyhydroxide powder(e.g., β-NiOOH, Kansai Catalyst Co.) and 42.97 g of a monohydratedlithium hydroxide (LiOH.H₂O, Aldrich Chemical) and heating the mixtureat about 210° C. in a tube furnace for about 20 hours under an oxygengas flow. The heated mixture was allowed to furnace cool to ambient roomtemperature, ground with a mortar and pestle, and re-heated at 800° C.for an additional 48 hours under flowing oxygen gas. The x-ray powderdiffraction pattern of the final reaction product corresponded closelyto that reported for stoichiometric LiNiO₂ (e.g., ICDD PDF No. 09-0063),as described, for example, in U.S. Pat. No. 5,720,932, J. Maruta et al.(Journal of Power Sources, 2000, 90, 89-94) and Y. Sun et al. (SolidState Ionics, 2006, 177, 1173-7).

Example 2 Synthesis of delithiated Li_(x)NiO₂

The lithium nickelate of Example 1 was delithiated by a low-temperatureacid treatment process similar to that disclosed in Example 1 of U.S.application Ser. No. 12/722,669, herein incorporated in its entirety.Specifically, approximately 100 g of LiNiO₂ was added to 1.5 L of arapidly stirred aqueous 6 M H₂SO₄ solution cooled to between 0 and 5° C.The resulting slurry is stirred and maintained at about 2° C. for eitherabout 20 hours (Ex. 2a) or 40 hours (Ex. 2b). Next, the suspended solidswere allowed to settle, the supernatant liquid removed by decantation,and the solid washed with aliquots of de-ionized water until the pH ofthe supernatant was nearly neutral (i.e., pH ˜6-7). The solid wascollected by either pressure or vacuum filtration and dried at about 80°C. in air for about 24 hours. The residual lithium content of the dried,delithiated Li_(x)NiO₂ product was determined by ICP spectroscopy to beabout 2.2 wt % Li, corresponding to x=0.31 (Ex. 2a) and less than about0.4 wt % Li, corresponding to x=0.06 (Ex. 2b). The x-ray powderdiffraction pattern of the delithiated product was similar to that ofthe stoichiometric LiNiO₂ with the expected shifts in the positions ofthe diffraction peaks to higher 20 angles. Average particle size of thedelithiated Li_(x)NiO₂ powder ranged from about 1 to 8 μm and the B.E.T.specific surface area was about 1.36 m²/g. The true density of theLi_(x)NiO₂ powder was measured by He pycnometer as 4.70 g/cm³.

The electrochemical discharge performance of the delithiated Li_(x)NiO₂was evaluated in 635-type alkaline button cells. Generally, button cellswere assembled in the following manner. Dried Li_(x)NiO₂ powder wasblended together manually with an oxidation resistant graphite (e.g.,Timrex SFG-15 from Timcal) and a KOH electrolyte solution containing35.3 wt % KOH and 2 wt % zinc oxide in a weight ratio of 75:20:5 using amortar and pestle to form a wet cathode mix. About 0.45 g of the wetcathode mix was pressed into a nickel grid welded to the bottom of thecathode can of the cell. A disk of porous separator material including alayer of cellophane bonded to a non-woven polymeric layer (e.g.,“Duralam” or PDM “PA25”) and saturated with electrolyte solution waspositioned on top of the cathode. Additional KOH electrolyte solutionwas added to the separator to ensure that electrolyte solution fullypenetrated the separator and wet the underlying cathode. A polymericinsulating seal was placed on the edge of the anode can. About 2.6 g ofanode slurry containing zinc alloy particles, electrolyte solution, anda gelling agent was added to the anode can. Next, the anode can with thepolymeric seal was positioned on top of the cathode can and the two cansmechanically crimped together to hermetically seal the cell.

Generally, cells were tested within 24 hours after closure. OCV valueswere measured immediately before discharge and are listed in Table 3,infra. Cells were discharged continuously at relatively low and highrates of 7.5 mA/g and 60 mA/g, respectively to a cutoff voltage of 0.8V. Gravimetric specific capacities (i.e., mAh/g) for cells discharged atlow and high rates are given in Table 3, infra. The capacity of thecells of Example 2b containing delithiated Li_(0.06)NiO₂ prepared fromthe LiNiO₂ of Example 1 and discharged to a 0.8 V cutoff at a 10 mA/gconstant current is about 150% of that of the cells of ComparativeExample 1 containing EMD (e.g., Tronox AB) as the only cathode activematerial. Further, the discharge voltage profile has two relatively flatplateaus with average voltage values of about 1.55 V and 1.35 V. Arepresentative discharge curve for cells of Example 2b is shown in FIG.10.

Example 3 Synthesis of Metal-Substituted Lithium Nickel Oxide,LiNi_(1-y-z)Co_(y)M_(z)O₂

Metal-substituted Li(Ni_(1-y-z)Co_(y)Al_(z))O₂ andLi(Ni_(1-y-z)Co_(y)Mg_(z))O₂ systems shown in the ternary compositiondiagram in FIG. 2 were synthesized, delithiated, and evaluated forperformance of the corresponding delithiated (i.e., lithium deficient)metal-doped nickel oxide active materials with regard to oxygen gasevolution, initial open circuit voltage (OCV), fresh (i.e., 24 hours)discharge capacity, and capacity retention after storage at ambient andelevated temperatures.

Metal-substituted lithium nickel oxides, LiNi_(1-y-z)Co_(y)M_(z)O₂(M=Mg, Al) were synthesized by blending 10.00 g of spherical β-nickeloxyhydroxide powder prepared by oxidation of a commercial sphericalβ-nickel hydroxide powder (e.g., Changsha Research Institute of Mining &Metallurgy, Changsha, P. R. C; Kansai Catalyst Co., Ltd., Osaka, Japan)by the method of Comparative Example 2 (infra) with stoichiometricamounts of a cobalt oxide (Co₃O₄, Aldrich, 99.8%) and either magnesiumoxide (MgO, Aldrich, >99%) or aluminum metal powder (Al, Acros, 99%) andlithium hydroxide monohydrate (LiOH.H₂O, Aldrich, >99%) to obtain thetarget atom ratios required for the desired compositions. The targetExample 3 compositions have the following Li:Ni:Co:M metal atom ratios:Example 3a 1:0.96:0.04:0; 3b 1:0.92:0.08:0; 3c 1:0.88:0.12:0;3c-1(M=Mg), 3d-2(M=Al) 1:0.98:0:0.2; 3e-1(M=Mg), 3e-2(M=Al)1:0.96:0:0.04; 3f-1(M=Mg), 3f-2(M=Al) 1:0.92:0:0.08; 3g-1(M=Mg),3g-2(M=Al) 1:0.96:0.02:0.02; 3h-1(M=Mg), 3h-2(M=Al) 1:0.92:0.06:0.02;3i-1(M=Mg), 3i-2(M=Al) 1:0.92:0.04:0.04; 3j-1(M=Mg), 3j-2(M=Al)1:0.92:0.02:0.06; 3k-1(M=Mg), 3k-2(M=Al) 1:0.88:0.10:0.02; 3l-1(M=Mg),3l-2(M=Al) 1:0.88:0.08:0.04; 3m-1(M=Mg), 3m-2(M=Al) 1:0.88:0.06:0.06;3n-1(M=Mg), 3n-2(M=Al) 1:0.88:0.04:0.08. All the mixtures weresimultaneously mixed by high-energy milling and heated to 210° C. at aramp rate of 0.5° C./min, held for 16-20 hours at temperature in an O₂flow, and allowed to furnace cool. The mixtures were simultaneouslyre-milled and re-heated under O₂ first to 105° C. (2.5° C./min) for 30min, next to 350° C. (4° C./min) for 3 hours, and finally to 800° C. (4°C./min) and held for 48 hours and then allowed to furnace cool toambient room temperature.

The products were re-milled and the overlaid x-ray powder diffractionpatterns are shown in FIGS. 3 and 4. The measured diffraction patternsfor the 26 metal-substituted lithium nickel oxides were consistent withthat of a layered α-FeO₂-type structure and comparable to that reportedfor a stoichiometric LiNiO₂ (ICDD, PDF#09-0063).

Elemental analyses of selected compositions of delithiatedmetal-substituted nickel oxide of Examples 2 and 3 (after acidtreatment) are summarized in Table 1. Samples of metal-substitutedlithium nickel oxides were acid-treated for two different periods oftime (e.g., 20 and 40 hours) to determine the relationship betweentreatment time and the extent of delithiation (i.e., lithiumextraction). All of the samples were treated simultaneously for the samelength of time and under the same temperature and mixing conditions tominimize variability. In general, most of the lithium ions appeared tobe removed during the first 20 hours of acid-treatment, nearlyindependent of the composition. However, removal of any portion of theremaining lithium during an additional 20 hours of acid treatmentsignificantly increased the total discharge capacity. Additional acidtreatment of selected samples of metal-substituted lithium nickel oxidefor up to 60 hours total did not substantially decrease the amount ofresidual Li nor increase discharge capacity in button cells. Residual Lilevels corresponded to an atom ratio of about 0.1 or less (i.e., <1 wt%) for acid treatment times of 40 hours or greater. In contrast, theamount of residual Li level after 20 hours of acid treatment wasgenerally greater than three times that for 40 hours (e.g., >2 wt %).

TABLE 1 Elemental analyses for a selection of layered metal-substitutedlithium nickel oxide sand the corresponding delithiated Ni (IV) oxidesand a Ni(OH)₂ precursor. Ex. Nominal Composition Delith. Metal atomratios No. of Precursor Time (h) Li Ni Co Mg Al 2a LiNiO₂ 20 0.31 1.04 —— — 2b LiNiO₂ 40 0.06 1.09 — — — — LiNi_(0.96)Mg_(0.04)O₂ 20 0.19 1.02 —0.04 — 3e-1 LiNi_(0.96)Mg_(0.04)O₂ 40 0.06 1.02 — 0.04 — —LiNi_(0.96)Al_(0.04)O₂ 20 0.30 1.01 — — 0.02 3e-2 LiNi_(0.96)Al_(0.04)O₂40 0.07 1.03 — — 0.03 — LiNi_(0.96)Co_(0.02)Mg_(0.02)O₂ 20 0.20 1.070.05 0.02 — — LiNi_(0.92)Co_(0.04)Mg_(0.04)O₂ 20 0.31 1.00 0.08 0.04 —3i-1 LiNi_(0.92)Co_(0.04)Mg_(0.04)O₂ 40 0.07 1.01 0.10 0.04 — —LiNi_(0.92)Co_(0.04)Al_(0.04)O₂ 20 0.13 0.99 0.08 — 0.04 —LiNi_(0.92)Co_(0.08)O₂ 20 0.33 0.96 0.12 — — 3b LiNi_(0.92)Co_(0.08)O₂40 0.12 1.00 0.13 — — 3m-1 LiNi_(0.88)Co_(0.06)Mg_(0.06)O₂ 40 0.08 1.020.07 0.10 — 3k-1 LiNi_(0.88)Co_(0.10)Mg_(0.02)O₂ 40 0.01 0.96 0.14 0.02— — Ni(OH)₂ — — 0.98 0.02 — —

Samples were measured using inductively coupled plasma atomic emissionspectroscopy (“ICP-AE”) by a commercial analytical laboratory (e.g.,Galbraith Laboratories, Inc., Knoxyille, Tenn.). Average particle sizesfor the metal-substituted lithium nickel oxides can be estimated fromanalysis of SEM micrographs. All of the synthesized compositionsexhibited strongly faceted crystallites ranging in size from about 1 to4 microns as shown for several selected samples in FIG. 5. All themetal-substituted lithium nickel oxide samples showed evidence for someinter-crystallite sintering resulting in the formation of largeraggregates composed of lightly sintered crystallites prior todelithiation. Specific surface areas (BET) of these aggregates wererelatively low, generally less than about 1 m²/g.

Example 4 Synthesis of Delithiated Metal-Doped Nickel Oxide,Li_(x)Ni_(1-y-z)Co_(y)M^(a) _(z)O₂

A 10.0 g portion of each of the metal-doped lithium nickel oxidesLiNi_(1-y-z)Co_(y)M^(a) _(z)O₂ (M=Mg, Al) of Examples 3a-n wassimultaneously stirred in separate 150 ml aliquots of 6M H₂SO₄ solutionheld at about 0° C. (e.g., 2-5° C.) for 20 hours and another portion ofeach for 40 hours. The delithiated solids were collected by filtration,washed with deionized water until washings had nominally neutral pH, anddried at 80° C. in air. The delithiated powders of Examples 4a-n havethe following nominal Ni:Co:M metal atom ratios: Example 4a 0.96:0.04:0;4b 0.92:0.08:0; 4c 0.88:0.12:0; 4d-1(M=Mg), 4d-2(M=Al) 0.98:0:0.2;4e-1(M=Mg), 4e-2(M=Al) 0.96:0:0.04; 4f-1(M=Mg), 4f-2(M=Al) 0.92:0:0.08;4g-1(M=Mg), 4g-2(M=Al) 0.96:0.02:0.02; 4h-1(M=Mg), 4h-2(M=Al)0.92:0.06:0.02; 4i-1(M=Mg), 4i-2(M=Al) 0.92:0.04:0.04; 4j-1(M=Mg),4j-2(M=Al) 0.92:0.02:0.06; 4k-1(M=Mg), 4k-2(M=Al) 0.88:0.10:0.02;4l-1(M=Mg), 4l-2(M=Al) 0.88:0.08:0.04; 4m-1(M=Mg), 4m-2(M=Al)0.88:0.06:0.06; 4n-1(M=Mg), 4n-2(M=Al) 0.88:0.04:0.08. X-ray powderdiffraction patterns of the dried solids were measured using Cu Kαradiation. Thermal stabilities of selected samples of delithiatedpowders of Example 4a-n were determined by DSC. The amount of residuallithium was determined for selected samples of delithiated powders ofExample 4a-n by ICP-EA and is shown in Table 1.

To assess the relative effectiveness of partial substitution of Ni byvarious metal ions on decreasing the extent of electrolyte oxidation bythe delithiated metal-doped nickel (IV) oxides, the amount of evolvedoxygen gas was measured as a function of time. Mixtures containing 60.6wt % delithiated metal-doped nickel(IV) oxide, 3 wt % graphite, and 36.4wt % alkaline electrolyte solution were placed inside laminated foilbags and heat-sealed closed. The bags were placed in an oven and held atvarious temperatures, for example, 25, 45 or 60° C. for pre-determinedperiods of time. The total amount of oxygen gas evolved per gram ofdelithiated nickel (IV) oxide was determined by measuring the relativebuoyancy of the foil bag containing the trapped gas using Archimede'sprinciple after storage for 0.5, 3.5, 7, 14, and 21 days. Severalsamples of delithiated metal-doped nickel (IV) oxides havingrepresentative compositions were evaluated. All samples evolved oxygengas at 25° C.

Other materials having known gassing properties can be used as controls.For example, a sample of delithiated undoped nickel(IV) oxide evolvedthe largest amount of gas in the shortest period of time. After 3.5 daysat 25° C., more than 7 cm³ of oxygen gas per gram was evolved. In thesame period of time at the same temperature, less than 0.5 cm³ of oxygenwas evolved per gram of a commercial EMD. Further, during the sameperiod of time (i.e., 3.5 days), a delithiated cobalt-doped nickel(IV)oxide having a nominal composition of Li_(0.12)Ni_(0.92)Co_(0.08)O₂evolved the least amount of gas, about 40% of that evolved by thedelithiated undoped nickel (IV) oxide. In fact, the total amount ofoxygen gas evolved after 21 days at 25° C. was less than 4.25 cm³/gramfor the delithiated cobalt-doped nickel (IV) oxide or less than 50% ofthat evolved by the delithiated undoped nickel (IV) oxide. A delithiatedmagnesium-doped nickel (IV) oxide having the nominal compositionLi_(0.06)Ni_(0.96)Mg_(0.04)O₂ evolved less than 6 cm³/gram after 21days. A delithiated cobalt and magnesium-doped nickel (IV) oxide havingthe nominal composition Li_(0.07)Ni_(0.92)Co_(0.04)Mg_(0.04)O₂ evolvedabout 10% more total oxygen than the magnesium-only doped nickel (IV)oxide. The rate of gas evolution with time also decreased rapidly forthose compositions having the lowest amounts of total evolved oxygen. Itis believed that surface passivation could be responsible for the rapidcessation of oxygen evolution. Oxygen gas evolution test results forselected compositions are summarized in Table 2.

TABLE 2 Oxygen gas evolution at 25° C. by delithiated metal-doped Ni(IV) oxides Ex. Vol. gas evolved/g matl @ 25° C. (cm³) No. NominalCompositions 0.5 days 3.5 days 7 days 14 days 21 days 2b Li_(0.06)NiO₂5.8 7.2 7.6 8.4 8.6 4e-1 Li_(0.06)Ni_(0.96)Mg_(0.04)O₂ 2.9 4.4 5.7 5.85.9 4e-2 Li_(0.07)Ni_(0.96)Al_(0.04)O₂ 5.3 6.5 7.2 7.5 8.2 4i-1Li_(0.07)Ni_(0.92)Co_(0.04)Mg_(0.04)O₂ 4.1 5.3 5.9 6.2 6.5 4bLi_(0.12)Ni_(0.92)Co_(0.08)O₂ 3.1 3.2 4.1 4.2 4.4 C-2Li_(x)Ni_(0.8)Co_(0.15)Al_(0.05)O₂ — — 2.8 — —

Discharge performance of delithiated metal-doped nickel (IV)-containingoxides acid treated for at least 40 hours was evaluated in 635-typealkaline button cells. Formulation of the cathode mix included blendingthe delithiated metal-doped nickel (IV) oxide with an oxidationresistant graphite (e.g., Timrex SFG-15 from Timcal), and alkalineelectrolyte (9N KOH) in a 75:20:5 mass ratio. The total weight ofcathode mix in each cell was about 0.45 g. The anode contained a largeexcess of Zn slurry (e.g., about 2.6 g/cell). OCV values measuredimmediately after cell closure generally ranged from about 1.84 to 1.92V. Cells were held for at least about 24 hours at ambient temperature(i.e., “fresh”) to ensure thorough absorption of electrolyte byseparator and cathode. OCV values measured immediately before the startof discharge typically ranged from about 1.72 to 1.81 V. Generally,fresh OCV values appeared to be independent of dopant type and levelexcept for those compositions having high levels of Mg only. Cells weredischarged both at a relative low rate (e.g., about 7.5 mA/g of activematerial) as well as a relative high rate (e.g., about 60 mA/g of activematerial) to a 0.8 V cutoff voltage. Overlays of representative low-ratedischarge curves for button cells with cathodes including selectedcompositions of delithiated metal-doped nickel(IV) oxides having aconstant total dopant concentration are shown in FIGS. 6 and 7. Thelow-rate discharge curves characteristically have a single, relativelyflat voltage plateau ranging between about 1.5 and 1.6 V. Averagedischarge voltage (i.e., CCV at 50% depth of discharge, viz. “50% DOD”)decreased monotonically with increasing cobalt level (i.e., in absenceof Mg or Al). Highest values of average discharge voltage were obtainedfor compositions containing Mg or Al and little or no Co. Post-storagecapacity retention was determined for button cells discharged at lowrate after holding for 1 week at 25° C. and 45° C. Average dischargecapacities, OCV, and average discharge voltage for all 26 synthesizedcompositions of delithiated metal-doped nickel (IV) oxides aresummarized in Table 3.

TABLE 3 Discharge capacities for alkaline button cells with cathodescontaining selected delithiated cobalt/magnesium/aluminum-doped nickel(IV) oxides. High rate CCV Low rate capacity capacity Ex. Nominal OCV7.5 mA/g (7.5 mA/g) (60 mA/g) No. Compositions 24 h, 25° C. 50% DOD 24h, 25° C. l wk, 25° C. 1 wk, 45° C. 24 h, 25° C. 2b NiO₂ 1.84 1.57 334317 277 381 4a Ni_(0.96)Co_(0.04)O₂ 1.78 1.53 364 321 379 4bNi_(0.92)Co_(0.08)O₂ 1.77 1.51 358 333 315 372 4c Ni_(0.88)Co_(0.12)O₂1.79 1.50 337 302 320 4d-1 Ni_(0.98)Mg_(0.02)O₂ 1.81 1.56 359 322 3634e-1 Ni_(0.96)Mg_(0.04)O₂ 1.70 1.57 365 347 307 387 4f-1Ni_(0.92)Mg_(0.08)O₂ 1.61 1.49 190 228 — 4g-1Ni_(0.96)Co_(0.02)Mg_(0.02)O₂ 1.79 1.56 322 287 345 4h-1Ni_(0.92)Co_(0.06)Mg_(0.02)O₂ 1.76 1.54 368 318 287 4i-1Ni_(0.92)Co_(0.04)Mg_(0.04)O₂ 1.71 1.55 373 362 — 387 4j-1Ni_(0.92)Co_(0.02)Mg_(0.06)O₂ 1.72 1.57 369 — 350 4k-1Ni_(0.88)Co_(0.10)Mg_(0.02)O₂ 1.81 1.52 303 265 370 4l-1Ni_(0.88)Co_(0.08)Mg_(0.04)O₂ 1.77 1.55 316 283 332 4m-1Ni_(0.88)Co_(0.06)Mg_(0.06)O₂ 1.78 1.58 347 318 368 4n-1Ni_(0.88)Co_(0.04)Mg_(0.08)O₂ — — — 293 — 4d-2 Ni_(0.98)Al_(0.02)O₂ 1.801.59 352 295 373 4e-2 Ni_(0.96)Al_(0.04)O₂ 1.78 1.59 363 236 323 3744f-2 Ni_(0.92)Al_(0.08)O₂ 1.80 1.57 286 242 383 4g-2Ni_(0.96)Co_(0.02)Al_(0.02)O₂ 1.76 1.56 359 302 373 4h-2Ni_(0.92)Co_(0.06)Al_(0.02)O₂ 1.76 1.53 342 301 328 4i-2Ni_(0.92)Co_(0.04)Al_(0.04)O₂ 1.81 1.56 340 294 340 4j-2Ni_(0.92)Co_(0.02)Al_(0.06)O₂ 1.75 1.57 351 292 383 4k-2Ni_(0.88)Co_(0.10)Al_(0.02)O₂ 1.78 1.52 338 302 355 4l-2Ni_(0.88)Co_(0.08)Al_(0.04)O₂ 1.79 1.54 360 318 374 4m-2Ni_(0.88)Co_(0.06)Al_(0.06)O₂ 1.78 1.55 340 266 333 4n-2Ni_(0.88)Co_(0.04)Al_(0.08)O₂ 1.72 1.57 360 316 338 C-3aNi_(0.9)Co_(0.1)O₂ — — 355 — — C-3b Ni_(0.8)Co_(0.2)O₂ 1.81 1.50 335 — —C-2a Ni_(0.8)Co_(0.15)Al_(0.05)O₂ 1.85 1.55 325 — — C-2bNi_(0.791)Co_(0.149)Al_(0.049) 1.83 1.55 335 — — B_(0.01)O₂

Button cells having the greatest low-rate (i.e., 7.5 mA/g) freshspecific capacities generally contained delithiated metal-doped nickel(IV) oxides having nickel partially substituted by a combination ofcobalt and magnesium and a total substitution level of less than about10 atom %. The average discharge capacity values generally ranged fromabout 365 to 375 mAh/g and corresponded to about 110-112% of that forcells containing delithiated undoped nickel oxide. Similarly, cellscontaining delithiated singly-doped nickel (IV) oxides in which thenickel ions were partially substituted by only cobalt, magnesium oraluminum ions at a level of less than about 5 atom % had specificcapacities that were up to about 108-109% of that for cells withdelithiated, undoped nickel(IV) oxide. Most of the cells containingeither delithiated singly or multiply-doped nickel(IV) oxides hadlow-rate discharge capacities that were either comparable to or slightlygreater (e.g., 5% greater) than control cells containing a delithiatedundoped nickel(IV) oxide. Further, cells containing delithiatedmetal-doped nickel(IV) oxides that had been acid-treated for 40 hours orgreater consistently had >80% higher capacities than cells containingdelithiated metal-doped nickel(IV) oxides acid-treated for only 20 hoursas shown in FIG. 8.

Button cells containing delithiated metal-doped nickel(IV) oxidesdischarged at a relative high-rate (e.g., 60 mA/g, 100 mA/g) hadspecific capacities that generally were comparable to or even slightlygreater than that of cells containing delithiated doped nickel(IV)oxide. Surprisingly, the high-rate capacities for nearly all the cellscontaining delithiated metal-doped nickel(IV) oxides were comparable to(i.e., 95-101% of the low-rate capacity) or even slightly greater (i.e.,104-114% of the low-rate capacity) than the corresponding low-ratecapacities. For several compositions having relatively high metal dopantlevels of either Mg or Al (e.g., Ni_(0.92)M_(0.08)O₂, M=Mg, Al), thehigh-rate discharge capacities were substantially greater than thecorresponding low-rate capacities. This is consistent with a relativelylow level of cell polarization and excellent high-rate performance forcells containing delithated metal-doped nickel (IV) oxides.

Post-storage capacity retention was determined for button cellscontaining delithiated metal-doped nickel (IV) oxides discharged atlow-rate after holding for 1 week at 25° C. and 45° C. Average dischargecapacities after storage at 25 and 45° C. as well as the correspondingcalculated percent capacity retentions are summarized in Table 4.Capacities of cells containing delithiated metal-doped nickel(IV) oxidesstored at 25° C. for 1 week and then discharged at low rate to a 0.8 Vcutoff generally ranged from about 85 to 95% of the corresponding freshcapacities (i.e., held for 24 hours at 25° C. before discharge).Capacity retention of cells stored at 45° C. for 1 week ranged fromabout 80% to 90% of the fresh capacities for nearly all the delithiatedmetal-doped nickel (IV) oxides. Capacity retention for cells containingdelithiated undoped nickel (IV) oxide was up to 83%. The highestcapacity retention (>90%) after storage at 45° C. was obtained for cellscontaining delithiated cobalt and/or magnesium-doped nickel (IV) oxides.

TABLE 4 Discharge capacity retention for alkaline button cells withcathodes containing selected delithiated cobalt/magnesium/aluminum-dopednickel (IV) oxides Low-rate Low-rate Capacity Low-rate Capacity Ex.Nominal capacity capacity retention capacity retention No. Compositions24 h @ 25° C. 1 wk @ 25° C. (%) 1 wk @ 45° C. (%) 2b NiO₂ 334 317 95 27883 4a Ni_(0.96)Co_(0.04)O₂ 364 321 88 4b Ni_(0.92)Co_(0.08)O₂ 358 333 93314 88 4c Ni_(0.88)Co_(0.12)O₂ 337 302 90 4d-1 Ni_(0.98)Mg_(0.02)O₂ 359322 90 4e-1 Ni_(0.96)Mg_(0.04)O₂ 365 347 95 308 84 4f-1Ni_(0.92)Mg_(0.08)O₂ 190 228 120  4g-1 Ni_(0.96)Co_(0.02)Mg_(0.02)O₂ 322287 89 4h-1 Ni_(0.92)Co_(0.06)Mg_(0.02)O₂ 368 318 86 4i-1Ni_(0.92)Co_(0.04)Mg_(0.04)O₂ 373 362 97 — — 4j-1Ni_(0.92)Co_(0.02)Mg_(0.06)O₂ 369 — — 4k-1 Ni_(0.88)Co_(0.10)Mg_(0.02)O₂303 265 87 4l-1 Ni_(0.88)Co_(0.08)Mg_(0.04)O₂ 316 283 90 4m-1Ni_(0.88)Co_(0.06)Mg_(0.06)O₂ 347 318 92 4n-1Ni_(0.88)Co_(0.04)Mg_(0.08)O₂ — 293 — 4d-2 Ni_(0.98)Al_(0.02)O₂ 352 29584 4e-2 Ni_(0.96)Al_(0.04)O₂ 363 236 65 324 89 4f-2 Ni_(0.92)Al_(0.08)O₂286 242 85 4g-2 Ni_(0.96)Co_(0.02)Al_(0.02)O₂ 359 302 84 4h-2Ni_(0.92)Co_(0.06)Al_(0.02)O₂ 342 301 88 4i-2Ni_(0.92)Co_(0.04)Al_(0.04)O₂ 340 294 86 4j-2Ni_(0.92)Co_(0.02)Al_(0.06)O₂ 351 292 83 4k-2Ni_(0.88)Co_(0.10)Al_(0.02)O₂ 338 302 89 4l-2Ni_(0.88)Co_(0.08)Al_(0.04)O₂ 360 318 88 4m-2Ni_(0.88)Co_(0.06)Al_(0.06)O₂ 340 266 78 4n-2Ni_(0.88)Co_(0.04)Al_(0.08)O₂ 360 316 88 C-2aNi_(0.8)Co_(0.15)Al_(0.05)O₂ 325 230 70 C-2bNi_(0.791)Co_(0.149)Al_(0.049) 335 — — B_(0.01)O₂

Cells containing delithiated cobalt and/or aluminum-doped nickel (IV)oxide generally had lower capacity retention than cells containingcobalt- and/or magnesium-doped nickel (IV) oxide for similar totallevels of substitution. No significant relationship between energyretention and OCV for cells held 24 hours at 45° C. was evident as shownin FIG. 9. Nearly all the cells containing delithiated metal-dopednickel(IV) oxides that had been acid-treated for at least 40 hours had arelatively narrow range of OCV values (e.g., 1.84-1.90 V) and hadrelatively high capacity retention values ranging from about 85 to 90%.

Partial substitution of other metal ions for nickel ions in delithiatedlithium nickel oxides having the general formulaLi_(x)Ni_(1-y-z)Co_(y)M^(a) _(y)O₂, where M^(a) is selected from cobalt,magnesium, aluminum, calcium, yttrium, manganese, and combinations ofthese, can produce a substantial decrease in the amount of oxygenevolved by the delithiated metal-doped nickel(IV) oxide compared to adelithiated undoped nickel(IV) oxide when immersed in alkalineelectrolyte at 25° C. Button cells containing delithiated cobalt andmagnesium-doped nickel(IV) oxides discharged fresh at low-rate can havespecific capacities up to 112% of that for cells containing adelithiated undoped nickel(IV) oxide. Low levels of residual lithium inthe delithiated metal-doped nickel(IV) oxides are desirable. Residual Lilevels corresponding to x<0.1 in the general formula are preferred,while residual Li levels corresponding to x<0.08 are more preferred.

Partial substitution of nickel ions by other metal ions also markedlyincreased the post-storage capacity retention for cells containing thedelithiated metal-doped nickel (IV) oxides relative to cells containinga delithiated undoped nickel(IV) oxide. Referring to Table 4, theimprovement in post-storage capacity retention was more significant forcells stored for 1 week at 45° C. than at 25° C. A total metalsubstitution level corresponding to 0.01≦y+z≦0.15, preferably0.02≦y+z≦0.12 in the general formula Li_(x)Ni_(1-y-z)Co_(y)M^(a) _(z)O₂is suitable, and a total metal substitution level corresponding to0.04≦y+z≦0.10 in the general formula Li_(x)Ni_(1-y-z)Co_(y)M^(a) _(z)O₂is preferred. Total metal substitution levels of y+z>0.15, preferablyy+z>0.12 are undesirable because the decreased amount (i.e., <85%) ofelectrochemically active nickel (i.e., Ni(IV), Ni(III)) results indecreased total specific capacity. Substitution of nickel ions bymagnesium ions is somewhat more effective than aluminum ions atdecreasing amount of oxygen evolution while increasing the specificcapacity and capacity retention, especially when present in combinationwith cobalt ions. However, substitution by cobalt only at relativelyhigh levels, for example, y>0.1, can result in somewhat greater freshcapacity than delithiated undoped nickel (IV) oxide, but substantiallylower capacity retention after storage at 45° C. Therefore, partialsubstitution (i.e., y≦0.1) of nickel by a combination of cobalt andanother metal such as magnesium or aluminum is preferred in order tomaximize fresh capacity, minimize oxygen evolution, and also maximizecapacity retention for cells with cathodes including delithiated nickel(IV) oxides.

Example 5 Pre-Discharge of Button Cells Containing Delithiated Ni(IV)Oxide

Button cells with cathodes containing delithiated, metal-dopednickel(IV) oxides were assembled according to the method of Example 2.Within about 1 hour after closure, the cells were discharged until aportion of the capacity equal to 5 or 10% of the total estimated and/ortheoretical specific capacity had been consumed. Some cells weredischarged at a relatively low-rate (e.g., 7.5 mA/g, 10 mA/g). Othercells were pre-discharged at a relatively high-rate (e.g., 60 mA/g, 100mA/g). Without wishing to be bound by theory, it is believed that higherrates can be advantageous because less capacity loss takes place duringthe time required to perform the pre-discharge. During pre-discharge,the cells were discharged at a constant drain rate, although in somecases, the cells were discharged intermittently (i.e., pulsed).Generally, pre-discharge was performed at ambient temperature. OCV wasmeasured immediately before pre-discharge then again after a storageperiod (e.g., 24 hours, 1 week, or 2 weeks), i.e., immediately beforedischarge testing.

To decrease the initial high rate of oxygen evolution immediately aftercell assembly, and to decrease or suppress parasitic self-dischargeprocesses that can occur during storage at ambient as well as elevatedtemperatures (e.g., 45° C., 60° C.), button cells with cathodesincluding delithiated metal-doped nickel(IV) oxides were assembled asdescribed in Example 2 and pre-discharged within 1 hour after assembly,at either low (e.g., 7.5 mA/g, 10 mA/g) or high rates (e.g., 60 mA/g,100 mA/g), until about 2.5%, 5%, or 10% of the total design capacity(e.g., about 7.5 mAh/g, 15 mAh/g, 30 mAh/g, respectively) had beenconsumed. For example, CCV values during pre-discharge for cellspre-discharged by 2.5% and 5% of their estimated design capacity (e.g.,about 300 mAh/g) were about 1.62 and 1.58 V, respectively, compared toan initial OCV value before pre-discharge of about 1.86 V. Afterpre-discharge, OCV values of the cells recovered to 1.73 and 1.72 V,respectively, and were constant for >110 hours as shown in FIG. 11. Suchan OCV value is comparable to that for NiOOH/Zn alkaline primary cells.

Button cells including cathodes containing selected compositions ofdelithiated, cobalt/magnesium/aluminum-doped nickel(IV) oxides werepre-discharged at a low rate (e.g., 7.5 mA/g) by an amount correspondingto 5% or 10% of their estimated total discharge capacity (i.e., about300 mAh/g), immediately after cell assembly. The cells were then storedfor one week at 25° C., 45° C. or 60° C. OCV was re-measured afterstorage immediately before low-rate discharge. The values are listed inTable 5 and can be compared to the corresponding initial OCV valuesmeasured prior to pre-discharge as well as the OCV values measured afterpre-discharge and recovery (i.e., at least 1 hour).

TABLE 5 OCV values after 1 week storage at 25° C., 45° C. and 60° C. foralkaline button cells with cathodes including selected delithiatedcobalt/magnesium/aluminum-doped nickel (IV) oxides and pre-discharged by5% or 10% of their capacity. OCV after Storage (V) Pre-discharge 5%Pre-discharge 10% Pre-discharge Ex. 0% 5% 10% 1 wk 1 wk 1 wk 1 wk 1 wk 1wk No. Nominal Compositions 1 hr 1 hr 1 hr 25° C. 45° C. 60° C. 25° C.45° C. 60° C. 2b Li_(0.06)NiO₂ 1.86 1.78 1.72 1.77 1.91 1.70 1.73 1.891.70 4e-1 Li_(0.06)Ni_(0.96)Mg_(0.04)O₂ 1.84 1.78 1.72 1.77 1.90 1.701.73 1.88 1.71 4e-2 Li_(0.07)Ni_(0.96)Al_(0.04)O₂ 1.88 1.84 1.75 1.801.76 1.72 1.76 1.75 1.72 4i-1 Li_(0.07)Ni_(0.92)Co_(0.04)Mg_(0.04)O₂1.87 1.82 1.72 1.79 1.74 1.71 1.75 1.73 1.71 C-2aLi_(x)Ni_(0.8)Co_(0.15)Al_(0.05)O₂ 1.85 --- --- --- --- --- tbd tbd ---

Prior to pre-discharge, the initial OCV values ranged from about 1.84 to1.88 V or higher, which is above the potential needed to breakdown waterand evolve oxygen. After pre-discharge by about 10% of the totalestimated capacity, OCV for alkaline button cells with cathodescontaining Li_(0.07)Ni_(0.92)Co_(0.04)Mg_(0.04)O₂ was lower than theinitial OCV by up to 150 mV. After 1 week storage at 25° C., the OCV hadrisen by only about 30 mV. Further, after 1 week storage at either 45°C. or 60° C., the OCV was still nearly identical to that afterpre-discharge (i.e., 1.72 V). In the case of a delithiated, undopednickel (IV) oxide, the initial OCV decreased by nearly 140 mV after a10% pre-discharge. The OCV value was maintained after storage for 2weeks at 25° C. or 1 week at 60° C. However, a 5% pre-discharge wasinsufficient to decrease the OCV of most compositions to below about1.80 V after pre-discharge. Further, cells pre-discharged by 5% had OCVvalues after 1 week storage at 60° C. nearly identical to those forcells pre-discharged by 10%. However, cells pre-discharged by 5%typically had higher OCV values than cells pre-discharged by 10% after 1week storage at 25° C. or 45° C. Therefore, a pre-discharge of about 10%of the total estimated cell capacity can be applied in order to decreasethe OCV of cells with a cathode including a nickel(IV)-containing oxideto a value comparable to that of NiOOH/Zn cells.

Example 6 Pre-Discharge of Button Cells Containing DelithiatedNickel(IV) Oxide

Button cells with cathodes containing delithiated, undoped nickel(IV)oxide were pre-discharged by 10% of their design capacity as in Example5, stored for one to two weeks at 25° C. or one week at 45° C. or 60°C., and discharged at a relative low rate (e.g., 7.5 mA/g) to a 0.8 Vcutoff voltage. As shown in FIG. 12, pre-discharged cells containingdelithiated undoped nickel(IV) oxide stored 1 week at 60° C. retained upto about 80% of the capacity for cells discharged 24 hours afterclosure. In contrast, cells that had not been pre-discharged retainedonly about 50% of their capacity after 1 week storage at 60° C. Toevaluate the effect of depth of pre-discharge on capacity retentionafter storage, button cells with cathodes containing delithiated undopednickel(IV) oxide and selected compositions of delithiated metal-dopednickel(IV) oxides were pre-discharged by either 5% or 10% of theirdesign capacity, stored for 1 or 2 weeks at 25° C. or 1 week at 45° C.or 60° C., and then discharged at low-rate (e.g., 7.5 mA/g) to a 0.8 Vcutoff voltage. Capacity retention was calculated as the percentageratio of the low-rate capacity of a cell discharged after storage for 24hours at 25° C. compared to that for a comparable cell discharged afterstorage for 1 or 2 weeks at 25°. Capacity retention values weredetermined for non-pre-discharged and pre-discharged cells containingdelithiated undoped nickel(IV) oxide and selected delithiatedmetal-doped nickel(IV) oxides that had been stored at 25° C. for 1 or 2weeks and are compared in Table 6.

TABLE 6 Capacity retention for alkaline button cells with cathodesincluding selected delithiated cobalt/magnesium/aluminum-doped nickel(IV) oxides after storage for 1 to 2 weeks at 25° C. with or without 5%or 10% pre-discharge Capacity Retention at 25° C. (%) Ex. 0%Pre-discharge 5% Pre-discharge 10% Pre-discharge No. NominalCompositions 1 wk 2 wks 1 wk 2 wks 1 wk 2 wks 2b Li_(0.06)NiO₂ 90 — 9491  97  96 4e-1 Li_(0.06)Ni_(0.96)Mg_(0.04)O₂ 95 — 95 93  95  93 4e-2Li_(0.07)Ni_(0.96)Al_(0.04)O₂ 95 — 97 91 — — 4i-1Li_(0.07)Ni_(0.92)Co_(0.04)Mg_(0.04)O₂ 97 — 98 91 100 100 4bLi_(0.12)Ni_(0.92)Co_(0.08)O₂ 93 — — — — —

Referring to Table 7, capacity retention values for cells containingdelithiated metal-doped nickel(IV) oxides having the same nominalcompositions as those listed in Table 6 that had been pre-discharged byeither 5 or 10% of their design capacity before storage for 1 week at 45or 60° C. were compared to those for corresponding cells containingdelithiated metal-doped nickel(IV) oxides having the same compositionsthat had not been pre-discharged before storage.

TABLE 7 Capacity retention for alkaline button cells with cathodesincluding selected delithiated cobalt/magnesium/aluminum-doped nickel(IV) oxides after storage for 1 week at 25, 45, and 60° C. with orwithout 5% or 10% pre-discharge. Capacity Retention (%) 0% Pre-discharge5% Pre-discharge 10% Pre-discharge Ex. 1 wk 1 wk 1 wk 1 wk 1 wk 1 wk 1wk 1 wk 1 wk No. Nominal Compositions 25° C. 45° C. 60° C. 25° C. 45° C.60° C. 25° C. 45° C. 60° C. 2b Li_(0.06)NiO₂ 90 83 54 94 96 77 97 96 764e-1 Li_(0.06)Ni_(0.96)Mg_(0.04)O₂ 95 84 — 95 98 84 95 100  88 4e-2Li_(0.07)Ni_(0.96)Al_(0.04)O₂ 95 89 — 96 86 77 — — — 4i-1Li_(0.07)Ni_(0.92)Co_(0.04)Mg_(0.04)O₂ 97 86 — 98 91 75 100  92 87 4bLi_(0.12)Ni_(0.92)Co_(0.08)O₂ 93 88 — — — — — — — C-2aLi_(x)Ni_(0.8)Co_(0.15)Al_(0.05)O₂ — 75 73

The use of pre-discharge as a conditioning method to increase capacityretention of alkaline cells with cathodes including delithiatedcobalt/magnesium/aluminum-doped nickel (IV) oxides was less effectivefor cells stored at 25° C. (i.e., ambient temperature) than for cellsstored at higher temperatures (e.g., 45° C., 60° C.). For example, cellswith cathodes including active materials having the compositions listedin Table 6 had comparable capacity retention after 1 week storage at 25°C. regardless of whether they were pre-discharged at 0%, 5% or 10% oftheir total estimated capacity. Further, the effect of pre-discharge wasrelatively small for cells stored for up to 2 weeks at 25° C.

In the case of cells stored for 1 week at 45° C. or 60° C., the cellsthat had been pre-discharged by 10% generally had better capacityretention than those not pre-discharged or pre-discharged by only 5% asshown in Table 7. Further, in the case of cells with cathodes containingdelithiated, undoped nickel(IV) oxide, capacity retention values forcells that had been pre-discharged by 0%, 5%, and 10% and then stored 1week at 25° C. were 90%, 94%, and 97%, respectively. The correspondingvoltage profile curves for cells discharged at low-rate after 5% and 10%pre-discharge are depicted in FIG. 13. For cells stored 1 week at 45° C.and 60° C., capacity retention was nominally the same (i.e., 96% and76%, respectively) for cells pre-discharged by either 5% or 10% of theirdesign capacity. In comparison, lower capacity retention values of 83%and 54% were obtained for cells that were not pre-discharged prior tostorage at 45° C. and 60° C., respectively. In addition, as shown inFIG. 13, the shape of the discharge curves for the cells stored at 45°C. differed significantly from those for cells stored at 60° C. Thisdifference supports the possibility that different parasiticself-discharge processes could be taking place at the two temperatures.Further, all button cells with cathodes containing a delithiated,magnesium-doped nickel (IV) oxide with the nominal compositionLi_(0.06)Ni_(0.96)Mg_(0.04)O₂ had the same capacity retention (95%)after 1 week storage at 25° C. independent of the amount ofpre-discharge. However, the beneficial effect of the pre-dischargeprocess was most evident for cells stored 1 week at either 45° C. or 60°C. Specifically, the pre-discharged cells had 98-100% capacity retentionafter storage for 1 week at 45° C. and 84-88% after 1 week at 60° C. Thecorresponding value for cells not pre-discharged and stored at 45° C.was only 84%.

Yet another example is provided by button cells with cathodes containinga delithiated cobalt and magnesium-doped nickel (IV) oxide with thenominal composition Li_(0.07)Ni_(0.92)Co_(0.04)Mg_(0.04)O₂ stored 1 weekat 25° C. Capacity retention values of 97, 98, and 100% were obtainedfor cells pre-discharged by 0, 5, and 10%, respectively. Thecorresponding discharge curves are depicted in FIG. 14. Capacityretention values for cells pre-discharged by 5% and 10% and stored 1week at 45° C. were 91 and 92%, respectively, and for cellspre-discharged by 5% and 10% and stored 1 week at 60° C., 75 and 87%,respectively. The corresponding value for cells not pre-discharged andstored at 45° C. was 86%. Thus, the combination of metal-substitutionfor nickel in delithiated Ni(IV)-containing complex oxides andpre-discharge of cells by 5 to 10% of their total design capacityshortly after assembly has been demonstrated to be particularlyeffective at decreasing the initial OCV as well as improving capacityretention after storage at elevated temperatures.

Comparative Example 1 Synthesis of β-Nickel Oxyhydroxide

A sample of spherical cobalt oxyhydroxide-coated β-nickel oxyhydroxidepowder was prepared from a commercial spherical β-nickel hydroxide(e.g., Kansai Catalyst Co., Ltd., Osaka, Japan) as disclosed by thegeneral method disclosed, for example, in U.S. Pat. No. 8,043,748.

A cathode mix was prepared by blending an oxidation-resistant graphiteand an electrolyte solution containing 35.3 wt % KOH and 2 wt % zincoxide with spherical β-nickel oxyhydroxide powder in a weight ratio ofnickel oxyhydroxide:graphite:electrolyte of 75:20:5. Button cells werefabricated by the general method described in Example 2. The cells ofComparative Example 1 were tested within 24 hours after fabrication. OCVmeasured immediately before discharge was 1.72 V. Cells were dischargedat about 10 mA/g constant current corresponding to a nominal C/30 rateto a 0.8 V cutoff voltage. Average discharge capacity for the cells ofComparative Example 1 was about 200 mAh/g.

Comparative Example 2 Synthesis of DelithiatedLi_(x)(Ni_(0.8)Co_(0.15)Al_(0.05))O₂ andLi_(x)(Ni_(0.8)Co_(0.15)Al_(0.05))_(0.99)B_(0.01)O₂

Samples of commercial lithium nickel cobalt aluminum oxide powders (TodaAmerica Inc., Battle Creek, Mich.) having the nominal compositionsLiNi_(0.8)Co_(0.15)Al_(0.05)O₂ andLi(Ni_(0.8)Co_(0.15)Al_(0.05))_(0.99)B_(0.01)O₂ (i.e.,LiNi_(0.792)Co_(0.149)Al_(0.049)B_(0.01)O₂) were delithiated by the acidtreatment process of Example 2 above to form the delithiatedmetal-substituted Ni(IV) oxides of Comparative Examples 2a and 2b,respectively. Button cells were fabricated by the general method ofExample 2. The cells of Comparative Example 2 were tested within 24hours after fabrication. OCV values ranged from about 1.83 to 1.85 V.Cells were discharged at a low rate of about 10 mA/g constant currentcorresponding to a nominal C/30 rate to a 0.8 V cutoff voltage.Discharge curves for cells containing the delithiated cobalt andaluminum-doped nickel oxide of Comparative Example 2a and the cobalt,aluminum, and boron-doped nickel oxide of Comparative Example 2b arecompared to those for cells containing the delithiated Li_(x)NiO₂ ofExample 2b and a commercial battery-grade EMD in FIG. 10. Averagedischarge capacities for cells containing the delithiatedcobalt/aluminum/boron-doped nickel oxides of Comparative Examples 2a and2b were 325 mAh/g and 335 mAh/g, respectively.

Comparative Example 3 Synthesis of delithiated Li_(x)Ni_(1-y)Co_(y)O₂(y=0.1, 0.2)

Samples of commercial lithium nickel cobalt oxide powders (e.g., NEICorp., Somerset, N.J.) having the nominal chemical compositionsLiNi_(0.9)Co_(0.2)O₂ and LiNi_(0.8)Co_(0.1)O₂ were delithiated by theacid treatment process of Example 2 above to form the delithiatedmetal-doped nickel(IV) oxides of Comparative Examples 3a and 3b,respectively.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, a delithiated metal-doped nickel(IV)-containing complex oxidecan be used as the active material in the positive electrode of anelectrochemical capacitor (i.e., super-capacitor, ultra-capacitor,pseudo-capacitor). In some embodiments, a delithiated or a partiallydelithiated nickel(IV)-containing complex oxide can function as anoxidation catalyst. For example, the complex oxide can be included inthe cathode of a metal-air battery, for example, a zinc-air cell. Insome embodiments, a delithiated nickel(IV)-containing oxide can functionas an efficient catalyst for breakdown of water to generate molecularoxygen.

In some embodiments, a delithiated metal-doped nickel(IV) oxide canfunction as the cathode active material in a rechargeable alkalimetal-ion battery, a rechargeable alkaline earth metal-ion battery, aprimary alkali metal battery or a primary alkaline earth metal batteryincluding an aqueous, non-aqueous, polymeric or solid electrolyte. Thealkali metal can be selected from Li, Na, K, or a combination thereof.The alkaline earth metal can be selected from Mg, Ca, or a combinationthereof.

Other embodiments are within the scope of the following claims.

1. A method of making a primary alkaline battery, comprising: partiallydischarging an assembled battery at a continuous drain rate within aboutone hour of cell closure; maintaining the partially discharged batteryfor a period of time ranging from 1 to 24 hours at a temperature in therange of 25 to 70° C. to provide a pre-discharged primary alkalinebattery; wherein the pre-discharged battery has an open circuit voltagevalue of less than or equal to 1.75 V at 25° C.
 2. The method of claim1, wherein the pre-discharged battery has a capacity retention of atleast 95 percent of the capacity of a battery discharged within 24 hoursafter manufacture, after storage for at least one week at 25° C.
 3. Themethod of claim 1, wherein the pre-discharged battery has a capacityretention of at least 90 percent of the capacity of a battery dischargedwithin 24 hours after manufacture, after storage for at least one weekat 45° C.
 4. The method of claim 1, wherein the pre-discharged batteryhas a capacity retention of at least 85 percent of the capacity of abattery discharged within 24 hours after manufacture, after storage forat least one week at 60° C.
 5. The method of claim 1, wherein thepre-discharged battery has a decrease in oxygen evolution of at least50% compared to a freshly assembled battery.
 6. The method of claim 1,wherein the pre-discharged battery has an open circuit voltage value offrom 1.65 to 1.75 V at 25° C.
 7. The method of claim 1, wherein thebattery is partially discharged by 15 percent or less of a total batterydesign capacity within 24 hours after manufacture.
 8. The method ofclaim 1, wherein the battery is partially discharged by 10 percent orless of a total battery design capacity within 24 hours aftermanufacture.
 9. The method of claim 1, wherein the battery is partiallydischarged by 7.5 percent or less of a total battery design capacitywithin 24 hours after manufacture.
 10. The method of claim 1, whereinthe battery is partially discharged by five percent or less of a totalbattery design capacity within 24 hours after manufacture. 11.(canceled)
 12. The method of claim 1, wherein the battery is partiallydischarged at a low rate of 5 to 10 mA/g of active material within 24hours after manufacture.
 13. The method of claim 1, wherein the freshlyassembled battery is partially discharged at a high rate of 10 to 100mA/g of active material within 24 hours after manufacture.
 14. Themethod of claim 1, wherein partially discharging the battery comprises astep-wise discharge process.
 15. The method of claim 1, whereinpartially discharging the battery is performed at 25° C.
 16. The methodof claim 1, wherein partially discharging the battery is performed at atemperature of from 20 to 30° C.
 17. The method of claim 1, wherein thebattery comprises: a cathode comprising an oxide having a formulaA_(x)Ni_(1-y-z-w)Co_(y)M^(a) _(z)M^(b) _(w)O₂; an anode; a separatorbetween the cathode and the anode; and an alkaline electrolyte, whereinA is an alkali metal, M^(a) is a metal dopant, M^(b) is a non-metaldopant, 0≦x≦0.2, w is 0, or 0≦w≦0.02 and 0.02≦y+z≦0.25.
 18. A battery,comprising: a cathode comprising an oxide having a formulaA_(x)Ni_(1-y-z-w)Co_(y)M^(a) _(z)M^(b) _(w)O₂; an anode; a separatorbetween the cathode and the anode; and an alkaline electrolyte, whereinA is an alkali metal, M^(a) is a metal dopant, M^(b) is a non-metaldopant, 0≦x≦0.2, w is 0, or 0≦w≦0.02 and 0.02≦y+z≦0.25, wherein thebattery has an open circuit voltage value of from 1.65 to 1.75 V. 19.The battery of claim 18, wherein the capacity retention is more than 95percent after one week at 25° C.
 20. The battery of claim 18, whereinthe capacity retention is more than 90 percent after one week at 45° C.21. The battery of claim 18, wherein the capacity retention is more than85 percent after one week at 60° C.